according to Apple these might be your options, assuming you have the 2.6 Ghz.
1TB 5400 rpm hard drive, 750 gig 7200 rpm hard drive or a 512 gig SSD officially. Macsales says up to 1 TB ssd for $460, but this is my best guesstimate
I don't know if the Apple store for sure won't install it. All I can tell you is call them or find an Apple authorized place that will do that for you*cough* Tyrosys
*cough* *cough* maybe austin apple repair. or Austin Macworks, MacTronics or even the Apple Store Barton Creek/ Apple sotre The Domain
Of course I could be full of it, well, maybe half-full. I don't see why they couldn't do it. After all you have a MacBook, it's an Apple Product, and I'm sure they wouldn't mind the work and the money
so, give 'em a call-that's all
JB