I also have a T-99 in pretty good shape.
While not yet BIG collectors items, they are increasingly getting higher prices, when in good shape.
If your gun is "pretty good," today I'd advise against restoration, for unless you spend REALLY BIG DOLLARS for a very fine professional restoration, your efforts will only degrade the collector interest of the gun and its value. And a very fine professional restoration will cost far more than its value when done. Oh, yeah -- look for a matching bayonet, too. And maybe the dustcover, and the monopod.
Clean it thoroughly, don't use oil on the stock (they used lacquer), prize it, and take care of it. Be warned, however, that unless your house is well secured, a wall-hanger is easy pickings for a burglar, and they do get stolen.
Mine is a fine shooter (when I can find ammo) with one of the best military triggers I've ever encountered.
Try visiting
WWW.CRUFFLER.COM for a list of sites that may lead you to stuff about the Arisaka. (I've got a list of Arisaka sites at home -- I'm visiting from work this morning -- and I'll try to look them up tonight or tomorrow.)