Share your experience!
I was asking the same questions as you only a few weeks ago. I needed a new screen, rear glass panel and headphone jack and and these parts alone online were about £120. None of the phone shop type repairers I found would guarantee the waterproofing after the repair either. Sony refuse to give out estimates for standard repairs because they say "each case is different".
Anyway, I bit the bullet and sent it off to Sony (who use an external repairer called SBE in the UK) and I was pleasently surprised that my total bill for a new screen, rear glass panel and headport jack was £78.