Looks to me like somebody reflowed the joints at some point

Unfortunately, those aren't the joints that are problematic. It's the ones on the daughterboard.

Desoldering the board can be a bitch. If you don't have the proper tools (i.e. real desoldering equipment) its easy to lift the traces. Proceed with caution or send it out to one of the reputable board repair guys.

Thats not stock. It's not necessarily bad, but it's not stock.

If you have any movement on those socket legs, it'll never work reliably. Since the daughter board is easily removed cuz of the sockets, it might be wise to just buy one of the GPE solutions that Chris posted earlier. Even if the female part of the socket on the mpu might still have problems you'll still have the redundant solder points ( above the socket on your mpu) that are probably unmolested and you should be able to get a good connection there.

That's probably the cheapest, easiest solution with a pretty high probability of working.