Welcome to the site
They only made the 700XX in 2008 & 2009.
The aftermarket for these bikes are a little thin but there are some good parts available for them.
As for the rear tires you are very limited on what is available. Maxis & Kenda both make the 11" tires for these as well as the original Dunlops. Alot of guys swap the rear wheels with the ITP 10" wheels to get more tire options.
As for reliability I can't answer as mine only has around 25hrs on it. But it is a Honda and they usually have good reliability.
I also have an 1987 Warrior that I keep as a spare for my friends without quads to ride. There is way more available for the warrior because they made them for so many years.
2008 700XX - OMF Beadlocks w/Billet Centers & Reinforcement Rings, Kenda Kutters, CCP Steering Stabilizer, ASV F3 Levers, ODI Rouge lock-on grips, Houser Bounce Nerf Bars, Pro Armor skid pad, UNI Filter
2007 400EX - CCP Steering Stabilizer, GT Thunder 450R Shocks, 450R Rear Brake Conversion, YFZ450 Front Brake Conversion, ProTaper Bars, Rath Racing Nerf Bars, Alba Elite Bumper, ASV F3 Levers, ODI Rouge lock-on grips, UNI Filter, Kenda Kutters, Pro Armor skid pad, Armadillo Swing Arm skid pad