Sources for components

Emachine T2865, AMD Athlon XP 2800 1GB Ram. Just lost/replaced the PS, and apparently the PS damaged the motherboard (according to the CompUSA techs that replaced the PS.) 3 yr old system: Out of warranty. Factory OEM motherboard is $160. I've never fooled with replacing a m-board.

Suggestions? Should I consider upgrading to a newer processor (such as an Athlon 64)? I don't have a lot of $ but if I can move up a little for a little $ I can swing it. Sources for buying boards? So far two friends have suggested TigerDirect.com and Newegg.com.

Any suggestions/recommendations will be appreciated.