I have an aluminum frame bicycle (mountain bike, 21-speed) that I purchased some time in the late 90s, it's marked "Skykomish Eureka" (though I can't find any evidence that such a brand and model ever existed), and it is currently outfitted with Shimano 300LX components.
I believe that the rear shifter is giving up the ghost, as sometimes the lower (up) handle will go all the way back without "catching" whatever it's supposed to be catching in order to shift the gears.
I toyed with the idea some time ago of replacing the components with something more upscale (back then, it would've been Shimano EX, I guess...), but I never did it. Now, I'm wondering whether it's worth the effort. I put several hundred dollars into this bicycle back then, so I'm confident it's not merely a BSO, but technology has come quite a way since those days.
Beyond the basic components (hopefully just a couple derailleurs and shifters), would it also be possible to replace the existing short-arm cantilever brakes with the newer long-arm type (which I assume would increase braking power)?