I tried to replace the blue housing to silver before. There's pda file about how to change it properly. In my experience, the hardest part is how to remove the lcd from the housing(need a special tool for it), the rest is actually pretty easy.

Oh here's the instruction and pdf
http://forum.xda-developers.com/show....php?t=1086178
http://forum.xda-developers.com/show....php?t=1123609