I had a ten year gap so felt similarly. dS2 is 9 months old now.
Things I'd change/not change:
The sleepyhead etc are not SIDS approved no. SIDS advice is still "a firm flat surface" which those nest things are not. People use them anyway and no deaths have been attributed to them, so it's your call. Personally as I never had one for DS1 I didn't see the need, and didn't miss it.
I have a co-sleeper. It's the Waldin one from amazon. It works but has some downsides: fiddly to put up and attach to bed, the edges are stupidly sharp once baby is mobile, the mattress is borderline dangerous as is it so flimsy even a fitted sheet makes it shrink away from the edges of a cot. You can get a custom mattress made up from an online company though, and on balance if you do that it's worth it. I do like the slightly bigger size and nonrestrictive weight limit of this cot. With DS1 I had a converted normal sized cot and I'd do either again. Better either of these solutions than the next2me etc though, personally, unless you 100% commit to stopping co-sleeping by 6 months.
I haven't got any kind of snot removing device. Baby has so far not exploded or suffocated from too much snot.
Baby bouncers are too upright these days, and the footrest not long enough to bounce comfortably. Bite the bullet and get the baby bjorn, because it's the only thing like the 80s ones, even though the one you probably had before for about 25p at a car boot sale will be better. You just can't find the old fashioned ones any more.
Angelcare bath seat did look really good, but both times I just plopped the baby in with Dad.
Car seat regulations have changed a little bit. If you understand anything from when you were shopping for your older 3, you'll be at a headstart compared to modern new parents who are bombarded with the entire set and no context to any of them. The biggest change is that in addition to the group/weight rating system, you can now buy car seats which are rated as suitable for different ages of child by height. These car seats will be labelled i-size, which means they've done a slightly more stringent crash test and in theory they are more universal than isofix, meaning for any new car which is i-size rated, any isize seat fits any isize car. "Group" type car seats are still legal to buy and use.
Car seat options have increased massively, which can be a bit of a minefield. It would be a really good idea to consider keeping your baby rear facing once they outgrow the baby seat, as it's much safer. Up until about a year (including past the first birthday) you're talking life and death even in a mild crash - to the point that under the new isize rules, it's now illegal to forward face before 15 months. (With a Group 1 seat it's legal, but not recommended by experts.) Rear facing seats up to about the age of 4 are now widely available and affordable, though, it's not some fringe thing any more. Impact shields are out as they never really became the new big thing. You can get lie-flat seats for newborns now which are safer than carrycots, which is useful as guidelines have changed to say newborns (up to 4 weeks) should not be in a normal car seat for longer than 30 min stretches at a time, and over 4 weeks up to 2 hours. Be wary of own-brand seats and super cheap seats, these are now flooding the market, get pushed heavily by retailers yet perform terribly in crash tests and tend to be hard to fit securely. Britax and Maxi Cosi still have a good reputation, so do Cybex, and Joie is the newcomer who do premium (safety) features for bargain prices.
Amazon has become a bit of a minefield for baby stuff as it is so full of Chinese sellers (some of who mock up a UK trading address...) in a not immediately obvious way, so I would no longer consider it a trusted retailer, but tread carefully. Bear in mind if you buy from outside the EU you may be circumventing safety standards we take for granted, like toys for babies not containing choking hazards or dangerous chemicals, stairgates having a certain strength, etc, and claims made on listings (BPA free, CE marked) not necessarily true. To be honest I am not 100% sure the Waldin cot I have meets British Standards. It came from Germany so I thought it would be OK. In future I'd check that whatever brand I'm thinking of buying is also available from a normal shop like mothercare, argos, etc, even if I do ultimately buy on amazon. However, the amazon brand baby wipes are well worth it especially if you do them on subscribe and save. S&S good for big boxes of nappies as well, especially if you use something like Pampers at night.
Apps can be brilliant but can be a bit crap as well. I like the white noise app (we use Baby Sleep - no ads, timers, fading rather than sudden start-stop, variety of noises) and a milestone recording app can be useful especially if it auto-exports to Facebook or whatever so you can look back on it later. I also really like Huckleberry, once you're out of the newborn fog and you want to see how sleep is going, you can use it to track sleep (don't bother tracking feeds and nappies) and it somehow magically predicts the next nap time for you and it REALLY WORKS. If you get close to the desperation of hiring a sleep consultant, you can even use the paid version of this app to get a "sleep plan" which has worked well for some of my MN group. But the free version is fine. Less good: All manner of apps encouraging you to track how many minutes you have breastfed off each boob. Oh my life. Just don't. Wonder weeks - useless, unscientific potrayer of doom.
Buggies now all seem to cost a million pounds (they were expensive enough in 2008, but now it's unreal) and they all have weird moulded solid seats for the toddler bit which is no use because if you want to recline them their legs end up in the air and they can't stretch out nice and comfy. Shop around, look past the headlines of "best sellers", and get something with a proper hinged seat. Again Joie are a brilliant cross here between cheap and good quality.