I've gotten lots of good advice on repairs for various cars over on Automotive Forums.
Here's the Sequoia forum:
Sequoia - Automotive Forums .com Car Chat
Glance through the first few pages. If you see the same issue in the thread titles repeatedly, consider that a common problem and decide if it's a big one or not to you. Something silly like "windshield washer hose clogged" or the like wouldn't keep me from buying a model, but a lot of transmission issues would.
ETA: I read through some of the Sequoia posts. I saw nothing that concerned me. The common question is how to program the remote garage door openers. It's not a very active forum, which could mean 2 things. there aren't many problems, or people who own a Sequoia don't do their own maintenance. The Jaguar forum is a good example of this. Very few threads relative to other brands, even for their smaller sales volume.