I wouldn't try that only because your button is going to be pretty hard to press, and might not work at all, if you use that gasket. The iPhone 4 home button really isn't that difficult, use a splunger to gently peel underneath the ribbon where it first makes contact with the plastic. When connecting the pins use a pair of tweezers, they are a HUGE help. Hope that solves your issue.
Have him take a look at the battery connector to see if he accidentally lifted the pins off of the board itself, there are four pins and sometimes people will pry them off if they are in a rush or not extremely careful.
AMAZING! Thanks for getting this out there! I've suspected that this phone was going to be easier to replace the screen ever since the leaked parts started pouring in.
Thank God it's not like the iPod Touch 4th Gen display.
When are you going to do a tear-down on the 5th Gen iPod touch?