Second the screws are a shame the reusing of them is a gambling game moreover they are setscrews within plastic. Screw heads wear out really fast because to soft material.
In the third place most of the parts are firmly connected with the housing, eg. the LED light, a few seals, some sheet metals, etc. Most of them you have to inherit to the new housing because of the lack within the new housing. With that in mind water resistance is gone, too.
Conclusing: The Motoroly Defy is a disposable device. The repair is too expensive (not even in money) and water resistance isn't guaranteed either. So buying a new phone or a barely used one is far easier than to try a repair of the old one. Too bad, but thats the way of market economy.