Can you replace the battery
Is the battery replaceable over the life of the macbook or are you out of luck when the battery life degrades past a usable amount.
2.0GHz, 2.3GHz, or 2.6GHz quad-core Intel Core i7 processor (Turbo Boost up to 3.8GHz) with 6MB shared L3 cache.
For some reason Apple decided to glue the battery cells to the top case in this system.
Apple does not sell the battery pack alone only as part of the top case assembly (P/N 661-6532) which is quite expensive! (around: $180 used & $600 new).
There are a few dealers of the battery unit alone. As reference: LaptopBatteryExpress for around $130.
If you do try swapping the battery be very careful! Make sure the battery is discharged, use a adjustable temp heat gun to soften the glue, a set of plastic spatulas and lastly have a chemical fire extinguisher handy! You may need it if you pierce a cell.
I got one of these in this week with a wine spill. An uppercase replacement part priced out at around $700. I took a hypodermic syringe and filled it with methanol and shot about 3 cc of it around each of the batteries. Let it sit for 10 minutes and rocked it a few times to get the alcohol as deep as possible. Then I used a putty knife. I inserted it on the outside batteries first from the side closest to the keyboard. As each battery came up I laid it back. It took less than 5 minutes to have the battery out and in good shape. Looks like prices run from $75 to over $150 for replacement batteries. On mine I needed to replace the keyboard but that's another story. I found a new part in China with keyboard for $158. I'll end up with a new upper case replacement and save $525 making the repair feasible. New trackpads are also available on eBay.