Service intervals should be something like 600, then 7500, then every 7500 after that. So, it should have had one at 15,000 and the next one would be due at 22,500. (The 1G bikes may have been a little lower than that, but 7500 is OK.)
Service should entail an oil change (which should happen more frequently than 7500 miles), fresh spark plugs, check the valve adjustment and correct any out of tolerance, clean or replace the air filter, check that everything is tight, fluids (brakes and forks) are clean, check steering head bearings, swingarm and susupension for slop, that sort of thing. Some of this stuff may be things you're already taking care of on your own schedule.
The cam chain has an automatic adjuster.