There weren't any different revisions in the sense that some GPUs failed and they fixed the issue later on.
What I can advise is that it's mostly a bad idea buying tech that old, especially when there's a dGPU. Historically the failure rate for dGPUs in laptops are considerably higher than iGPU only.
Also the computer really isn't that powerful any more. Even the top BTO 2.8GHz i7 in that 15" Mid-2010 has less power than the lowest Core M in the current Retina MacBook. Same story for the graphics.
Literally any brand-new Mac would offer better hardware performance in every aspect (quicker I/O, RAM, CPU, GPU) than that machine. You'd be better off buying new or refurb.