Should I even consider a new TV with repaired lot damage?

If you can't spot the fix then 99% of the public probably wouldn't be able to spot it either. If it cost $900 at a dealer's rate then there couldn't have been that much damage.

Use your knowledge of the repair to try and get a lower price. If you're going
to keep it for a long time I'd still try to get it if the price is right.

Sounds like you've got an honest dealer especially if it didn't make it to Car Fax.