You're going to have trouble finding a high-quality fork in 1". Unfortunately the suspension manufacturers have left 1" headtube bike owners behind. There might, however, be a solution.
But before getting to that, you should consider the advantages & drawbacks of doing so. Your frame was manufactured without suspension mind (an assumption on my part based on its age). Putting on any suspension will lift up the front end, thus changing (reducing) your head tube angle and affecting the ride of the bike. Especially any fork with over 80mm travel. Your bike will exhibit less responisve steering. Talk to your LBS and have them determine if the ride quality will suffer too much.
The next issue is that you probably won't be able to find a threaded 1" replacement. Going threadless is a nice upgrade, but will involve replacing the stem and headset. If the bike is still stock and equipped with quality stem and headset, you may want to rethink. Additionally, you probably still have cantilevers, which require a cable stop. Today's suspension fork braces no longer have brake cable stops. So, to obviate the necessity of a cable stop, you'd have to upgrade to V-brakes. Now you're talking replacing brakes and brake levers. Time to reconsider!
And the above argument assumes you'll be able to get a quality 1" fork in the first place. Well, I know of a frame builder who was considering offering fork steer tube replacement. Specifically, replacing the stock 11/8" with a 1". It's relatively easy replacing them in most forks - you just need the appropriate tooling and a replacement steer tube that reduces down to 1" after exiting the fork crown. Kelly Bike Co. (
www.kellybike.com) was considering offering this service, but I don't know if they ever started it. You may find someone else in your area who can do this for you.
Given all the difficulties, I'd keep the bike stock and enjoy it for what it's worth: an excellent rigid hard tail. And being on the "wrong end" of 35 (like myself!), you would probably benefit even more by going with a nice cross country full suspension bike. All my riding buddies who've taken the plunge, have done so happily, never intending to go back. (I'm still holding out, however.)