Steven,
Couple of issues that may or may not make this a good deal.
1) Price if firm, no budging: Okay...that's fine, but make sure it is what you want. The second part, "plenty of buyers"...then where are they? If it was that hot of a ticket, I would expect the plane to be gone.
2)Based on item #1 and seeing no "sight unseen buyers" in sight <img src="/ubbthreads/images/graemlins/smirk.gif" alt="" />, don't pay the deposit. Call them in the morning of your departure and make the 50 mile trip. I would NOT in this case put non-refundable money up. That does NOT sound typical.
3) I can see where they don't want to be flying the airplane around for someone to criticize, so this does not scare me in and of itself, but you will have some investment in your AP going to look at the bird. He probably can do this with a minimum amount of tools.
Thoughts, don't get too passionate here or you will make a wrong decision.
How about if your AP goes up immediately and confirms the condition and airworthiness (maybe flies the plane for you) THEN you put up a deposit to hold it until you decide if you like the colors? Just a thought.
Oh...both a GPS and Loran, or is the GPS yoke mounted? That does not add much to the aircraft value. Any guarantee/warranty on the "new limits" engine, or is it really a shop overhaul that adds less value to the aircraft? I wasn't clear on that.
I am a bit more philosophical in that, if it isn't meant to be, I don't want to force it, so I am generally opposed to non-refundable deposits unless I have already had a pre-buy or annual completed by an AP of MY chosing and am boarding an airliner. Truth is...people have backed out of deals even with a deposit, so it can be a false economy.