I just replaced mine but that's not easy as there's a lot of cables to remove, together with some PCBs.
The lithium battery is located under you battery compartment and to remove it, you have to open pretty much everything. You want to take your time, work by steps and use different small cups to store the screws for each step. You then want to remove the board and unsolder the old battery using the correct tools for the job.
If you're not familiar with electronics, I would not recommend it. Send it to a repair shop.
Otherwise, I'll be in Hong-Kong on the 19th of September for a week! ;>
