Hi Pieter,
I just did a near-complete teardown of the 2010 MBP thanks to tea. If you follow the upper case replacement guide you can get to the point where you can see the trackpad right away just by removing the battery.
Fortunately for me (but unfortunately for you), there didn't appear to be any tea around the trackpad area. However, from my experience inside the case, there's a *chance* you may be able to partially dissassemble the trackpad and do some cleaning that may remedy or mediate the issue.
In any case I would suggest pulling it apart for cleaning just to make sure there is no other damage that can become a bigger problem later on down the road. Take a look at the attached pictures and you can see that the trackpad has screws that you may be able to remove to do some deeper cleaning. You may also benefit from the info provided in the question and answers from my own tea spill :)
http://www.ifixit.com/Answers/View/24205/Liquid+Spill%2C+Should+I+perform+complete+teardown
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