I have 16 months between mine (not planned). They are now 2 & 3 and I have another due in July (also not planned, some serious permanent contraception to be booked asap).
My two are an absolute doddle now (making the thought of having a newborn again more than a bit daunting). Since DD started nursery she plays constantly with her brother and they make up so many games. Its incredible to watch.
It must have been hard (especially as my dad died a week before my second was born). But I honestly don't remember it being that bad. I have an incredible DH who works away but when he's home he's home. So I guess he was around for a lot of the first few months. Although he was gone almost constantly for 4 months when the youngest was 5 months and I still managed. Even starting part time work (from home) when he was 7 months.
For me the hardest bit was always loading 2 very small kids in/out of cars safely. (Thoroughly recommend the swivel car seats).
And like someone said, definitely get a good sling/carrier.
Also be prepared that your current DD will likely want everything you get out for the baby. Mine even started trying to breastfeed again (having been completely weaned for 6 months). Luckily we don't ever seem to have had any jealousy over here. Though I'm expecting some from DS when the baby arrives.
There were tricky bits like when the small one wasnt putting on weight and wouldn't take milk but a toddler made it very difficult to give the extra attention required. But honestly its amazing what you can manage when you need to. And i am by no means a super mum. My favourite pasttime is to sit down!
Good luck, but honestly you can do this!