When you do the memory re-seat, you need to make sure that the memory goes back into the appropriate slots - Bank 0 and Bank 1 need to have the same matched pairs in each of the...
Before you go re-seating the CPU's I'd look at the memory, I think that would be more productive. Pulling the CPU's is a bit more risky than the memory.
Just a quick bit of info, the server will only run Solaris up to and including Solaris 10 1/13 - it will not run 11 as the SPARC IIIi processor is not supported by the OS.