Dimension 2400 CPU

I damaged one of the pins of my Pentium processor in my Dimension 2400 trying to remove it & the heatsink (long story).  So can I upgrade the processor?  The online listing for my system says:

Pentium 4 Prescott DT Pentium 4 Cdart Mill

So I'm not sure exactly what all that means, but it has a large aluminum heatsink & no fan on it. 

What processor should I replace it with that will fit the socket?  Do I need to remove the heatsink and reuse it, and if so how?

Thanks!