I would tell the seller, that for that much money it better work. Just make sure you get a warranty with it.
Since it doesn't have a lot of miles on it, just make sure it rotates fine and isn't leaking any fluid. You never know where it was sitting in the salvage yard, so do be sure to look for any physical damage to the outside of the long block.
Since you're not planning to rebuild it, there isn't much for you to replace other than the spark plugs. You could replace the pcv valve and water pump, but those are optional. With the low mileage that it has, there is no need to change the timing chain, and as long as the previous owner did oil changes at regular intervals, the oil pump should be fine too. However I would definitely recommend that you change the oil after the first 20 miles, to flush out any old dirt and gunk that has been in the engine since the last time it was ran.