if you mean a broken screen, yes you can fix it easily.
And if you don't know how here's a manual http://www.ifixit.com/Guide/Installing+iPhone+3GS+Display/1542/1
answered Jan 04 '13 at 15:16
Yes it will require a restore though. Put it into recovery mode (look how to do it on google), then restore from iTunes. Boom done. Hope that helped :)!
answered Jan 04 '13 at 22:56