well if it was me i'd buy the car and just buy a replacement engine to put in it...
if you wanna see if the engine is siezed just get a ratchet with a 19mm socket and see if you can manually rotate the crank, if you can't then it must be siezed, you could also do a compression check if the engine does crank over, if it has an oil leak you can probably gaurantee that the engine will get rod knock if it hasn't already
you really need to be more specific on what you mean by the car won't move, does the engine start all fine etc but the car will not move forward in gear? is it manual or auto?
is the diff locked? jack up the rear end and see if you can move the rear wheels
really need more specifics... but let us know how you go
