No answers yet, so thought i would just add a few things......
Here is a guide for the upper case:MacBook Pro 15" Unibody Mid 2010 Upper Case Replacement
This is difficult as the guide says, it is NOT something i would recommend a person with no experience trying to tackle, unless they are just good at this kind of thing having repaired computer before....... Specials tools, easy to break connectors etc.
Entire computer needs to be taken apart to gain access to this area you need fixed.
I really don't know how much some thing like this would cost, Maybe someone else would have an accurate estimate?
if not fixing your self, you could check at the apple store however not sure they will void any further warranty work if under apple care.
Could also check for licensed or approved what ever the term is for apple repair places in your area, check online reviews for local places that do apple repair and have certified apple repair people ( not sure if you have a warranty or not from apple) and these local places should be less expensive........ and might be willing to work with you on parts, you may even be able to bring your own replacement part in.
Depending on how much new parts are, you can see how much a new top case ( with keyboard etc) is going for on ebay. Just have to make sure it's the correct model # part number etc and good sellers are usually helpful with that.
and of course however it ends up being fixed, keep that old top case and you you may be surprised how much you can sell it for on ebay even in non working condition, people always need/want this kind of thing working or not.
Lastly, what ever repair place you use, make sure the motherboard and other internals are inspected and cleaned so no water or corrosion from the water spill remains laying in wait to cause further problems.