Will i need a new motherboard?

You will definitely need a new motherboard because AMD processors don't fit in the same sockets as Intel processors, not since socket Super 7 and the AMD K6-500. If you can afford to then get a Phenom X4 or a Phenom II X4 rather than an Athlon, since the Athlon chips have no L3 cache. You'll almost certainly need a new PSU unless it has a high enough power rating - you don't want to spend all your money on new parts, just to risk damaging them with a PSU failure. It sounds like you're going to have to replace most of the machine so you might want to consider a new case too, although that might not be necessary if the parts fit and the ventilation is adequate.