Dont bother with Apple, its too easy a job to allow them to rip you off.
I have videos on YouTube showing you how to upgrade your HDD - check on them for guidance.
Go for any 2.5" HDD with a SATA connection (Samsung M8, WD Scorpio Blue are both pretty affordable at the 1TB mark - last time i checked the Sammy was only £65).
Failing that, I'm based in the UK so if you are not too far from me I dont mind doing it for you (the hardware side of things) - only takes a few mins.
Alternatively, stick the new 1TB drive into an external caddy (USB3.0 caddys are pretty cheap) - use SuperDuper to clone the current drive across to it, then swap the drives over and voila - you have all your data intact and ready to go on a 1TB drive, with no need to install everything from scratch!
Also bear in mind that both RAM and HDD's are user upgradeable parts - upgrading these will not void the warranty on the rest of your laptop (as long as you do not damage it during the install obviously).