I put in my own 27' overlap liner two years ago. Some advice from my experience.
Wall foam - it's nice I guess, but I would not go through the trouble and expense of it again. OK, so my walls are a little cushy. It's not as if I am slamming into them. I also dont see any increse in temerature retention. I guess it does protect the liner a bit, but really getting that stuff on straight, with spray adhesive, with the slightest breeze - not fun. If you do use it, you can get spray adhesive a lot cheaper are a hardware store, than from the pool supplu places.
Foam Cove - yes, yes, yes, and if I didn't say it, yes. Use it. I used the peel and stick. It works great, and makes a very nice cove
Floor pad - I decided not to use it. I did't have one to begin with. Regardless, I went over that bottom with a fine tooth comb. Somehow I still have a pebble under my liner. No idea how it got there. I don't mind the feel of a sand base, but I do hate knowing that pebble is there.
Liner - Get the right one for your pool (overlap, J hook, beaded, etc) and for the most part, you do get what you pay for. A $100 liner is going to be a gloified trash bag. Check the thickness.
Setting the liner, the shop vac method does work. If you are using an overlap, be careful of your walls when you take the top rails and track off. I put a crease in mine because I was trying to adjust the liner and I pulled the wall in.
Set the liner on a sunndy day - it helps.
Have help - it helps, liners are heavy
Don't rush - allocate plenty of time to get it done. work slowly and give yourself time to get the liner set correctly.
The goal is perfectly smooth, with no wrikles. I have two small wrinkles in my wall - I blame the foam, it bunched up. Still, you barely notice them.
I would put my own liner in again.
-dave