Don't feel guilty offering $900 for a NON WORKING F-14. I agree that something smells here. Don't assume any easy fixes.

Look it over good. I guarantee you will miss more than a few things in your excitement. Keep your inspection to 5 minutes or less. If you stand there for 40 minutes nitpicking, you're gonna irritate the guy and he'll stonewall you on negotiations.

If you like what you see, offer your $900 (or slightly less even) and have cash in hand and be ready to break it down/move yourself.

If you want it fixed (since he offered), then I offer this as a negotiating possibility. Look it over fast - 5 min or less again - and get him talking about what he thinks is wrong. After BSing a minute, tell him you'll give him $1000 if he fixes the issues (displays, and anything else he fesses up to), or $800 right now, as-is and you won't hear from me again.

Worst case is he says no, and in that case you should walk and be happy you did.

Good luck!