I had implants 5 years ago, just to go bigger, as I could feel my ribs through the top of my breasts after having 3 kids. I've had no problems and found the recovery a breeze, able to wash my own hair after a couple of days and driving again after 3 or 4 days. Some people find it much harder and aren't able to do these things for a couple of weeks, but my experience was good.
The majority of boob jobs end up very natural looking.
My advice would be to have consultations with at least 2 different surgeons, then you can see if the advice they give is similar, what their reasons are for the size/ placement they suggest for you, and make a decision on who you trust to do the op.
There is another forum called 'Breast Buddies' that I found helpful when I was doing my research.
To answer a couple of your questions-
I chose rounds, as I was shown when you hold a round implant from the top the gel fills the bottom slightly more due to gravity, like takes a slight tear drop shape anyway, so rounds allow a little more natural movement and remove the risk of a teardrop implant rotating.
I decided on size by literally describing to the different surgeons the 'look' I was hoping for, and they suggested an implant size (they are measured in cc's, you can't ask for a specific bra size). They suggested similar sizes so I was happy with that, and I did end up exactly as I wanted.
I think mine cost £4100 if I remember correctly.
I'm happy now, and I was overjoyed at first as well, but there have been times I've regretted going as big as I did. im around a 32ff and size 14, it sounds big but doesn't actually look it on my frame. I just had trouble coming to terms with the fact that I'd changed myself permanently... It's hard to explain as I got exactly what I wanted and had no complications.. It's probably just me being silly.
Future surgery is a worry, although the implants that are used now should last much longer than the 10 years they used to quote 10-20 years ago. I was told the premium implants May last a lifetime now, but most people will become unhappy with the look of them after several years due to ageing, sagging, wanting to change size, so will still have more surgery.
I'm rambling on now! Good luck