On the other hand, mountain bike technology has progressed so far since 1994, and prices are so good (due largely to overcapacity in the industry), that you might just be happier starting over. You might even be able to sell your Nishiki for $100 or $150, easing the transaction costs even further.
Regular readers will know that while I don't dismiss dual-suspension bikes, for most people I think they're more bike than is necessary and that the rear suspension jacks up the cost and weight. Hardtails are great buys, perform extremely well, and can be readily modified with the addition of a suspension seat post for near-dualie performance. Plus, for under $1,000, you can get some really nice bikes. An example: Marin's Eldridge Grade ($1,000), which has a super-smooth steel frame, a bump-eating Mars front fork, and smooth-shifting Shimano XT and Deore components. Another example: Raleigh's M600, just $780 for a light aluminum frame, and even includes disc brakes. If you wish, you even can go with dual suspension for under a grand and get a pretty decent bike, such as the K2 Bumpy Monkey (OK, it's $1,200, look for a sale). But compared with, say, the Eldridge Grade the component group isn't quite as good, and the bike weighs two to three pounds more.