Please give Advice on a big decision! Long Post!

You can plan that any extended warranty will contest the repairs and want to know every detail. Lack of improper maintenance isn't covered. Like mice eating your wires and associated damage - they won't cover it. Normal maintenance isn't covered and it sounds like you might be needing a lot of that, as it wasn't taken care of. Some are a real problem for the dealers to get approval on repairs. Been there done that. Watch your deductible.