8 years isn't bad if it's been in use. Sitting dry for 8 years, I would pass.
Also depends how it's been stored, how many times it's been moved, etc. I have had newer tanks leak (especially cheap Aqueon ones), mostly smaller ones, if moved with barely any water in them, or crack fairly easily, etc. Like Blair said, look at the seals, if they look solid with few to no bubbles, silicone not peeling up, etc, it should be fine.
For peace of mind talk to the guy Blair and others have used and get a reseal with nice black silicone...for a good sized tank it's well worth not worrying about it leaking.