Trackpad got so that I had a very small and hard-to-click clickable area on my mid-2009 macbook pro. Replaced battery according to ifixit guide and purchased and used the suggested tools. Trackpad now clicks like new.
Went as easy as suggested in the ifixit guide. I bought all of the recommended tools. All screws went back in pretty easily. I didn't notice any differences among the different short screws.
I live two blocks from a very good Apple store, but the battery was so easy to replace at home that I'm glad that I didn't bother taking it to the Apple store and surrendering it, even if for just a half hour or so (repair took less than 10 minutes). Wish I had done this repair months ago.