I don't know the value, per se, but I'll buy almost any game that is complete and half decent for $250-$300.
Being that it's your first EM machine, the better it looks on the inside would be of more significance to me than the outside, to a point.
Learning about these things on a complete semi running machine is a ton easier than trying to resurrect a basket case. They can overwhelm you quickly. Read up on schematic reading and tune up your soldering skills! Get a decent Volt/Ohm meter too.