I've never had the late model "push-to-cancel" units apart to check, but on the early model bikes like yours the switch is easily serviced.
There is a detent ball and spring inside the t/s switch. As long as nothing is bent, broken or missing you can take the switch apart, clean the switch contacts and clean and lube the detent arrangement with some dielectric grease and be good to go for another ten years. YMMV.
While you're in there you can also clean up horn button and headlight hi/low switch, as well.
There really isn't much to the switchgear. Once you get ito it you'll see how simple it is. But I recomend that you NOT try to work on it while it's still on the bike. Unplug it and remove it. Take it apart while it's inside a large cardboard box, or maybe work on it inside a large trash bag er sumpin'. The switch may be simple, but ff this is your first time taking one apart you may launch either the spring, the detent ball or one of the smaller screws into a black hole. You won't easily find replacements for any of those.
There's a lot of aftermarket and Yamaha switchgear which are functionally identical to the left switchgear of a TW. Most of the early XT stuff will plug right in and all of their guts will swap with early TW switchgear guts.
The right side kill/starter button switchgear is a bit of a different story because most modern bikes have a master cylinder which dictates a different orentation of the switchgear relative to the throttle cables. Some of the early stuff with drum brakes is oriented correctly but has no e-start button, etc.