Good deal! If you see anything that hints at trouble (splines are damaged, dropped and pan is crushed in, broken tab or something on the case, etc...) make sure you point it out to him. Just make sure its something that you are comfortable buying. If its a total basket case, I'd low ball him even more.
Like you said pull the pan for sure. From what you said above, it sounds like it was rebuilt but never used or had oil put into it. IIf that is the case the filter would be brand new and clean as will the inside of the pan. If it is dirty, that tells you something. Spin the input shaft and output shaft to make sure everything is free inside. Move the shift lever thru the gears to make sure that works. That is really about all you can do
I would not pull the pump while there. If you want to do that, do it when you get home. That is where I suggested having a trans shop look it over if you are not comfortable going thru it. As soon as you pull that pump you will more than likely wreck the gasket and will need a new one anyways. Not to mention the guts will probably shift inside.
