i did mines my self its very easy and there are plenty of youtubes to show you and it would cost way less 😀
I bought a $10 back off eBay and installed it myself. It was a royal pain because of the bazillion screws and pieces though.
I'd say it's comparable to replacing a hard drive on an iBook, which ain't easy.
How cracked are they? Like, falling-apart, or just a little bit? A little super glue and some sanding/wet-sanding/polishing might get it looking "good enough" for just a few bucks and some elbow grease.
http://forums.macrumors.com/showthread.php?t=871308
I bought a $10 back off eBay and installed it myself. It was a royal pain because of the bazillion screws and pieces though.
I'd say it's comparable to replacing a hard drive on an iBook, which ain't easy.
Here's the guide for doing it. Doesn't look too hard but it will take a bit of time and patience.
http://www.ifixit.com/Guide/Installing+iPhone+3G+Rear+Panel/583/1