I have a mid 80's Schwinn High Sierra bike that has the following equipment:
Shimano RD-MT60 rear derail, Shimano FD-MT60 front derail, it has 3 speed front gears and 6 speed rear gears, the shifters are Shimano SIS that are broken.
This bike has been hanging in my garage for 8 to 10 years and I am getting old and fat and need to ride the thing. I would like to update the bike somewhat to the easier shifting mechanisms that I have seen on other bikes. Can this be done without changing everything on the bike?
Mikecool

No one makes 6-speed stuff anymore. You'd have to find it used somewhere. If it was me, I'd just buy a new bike.

He's right you can find upgrades in 6 spd stuff but it takes knowledge to know what to get, time to hunt it down usually through the net, and probably for too much money.
But....
Here in Seattle we have a really neat bike store named Recycled Cycles, where people bring down old bikes and trade them in for new goodies, if you had a place like that around your neighborhood that would be the first place i'd look, but your gonna have to sift through and probably settle for used product, not that in some cases that's bad however.......
If you do decide to scrap your old bike (perhaps there's more problems than meets the eye), now would be a good time to jump on a new entry level bike. Price of metal is jumpin a tad since China is gobbling it up being the industrial behemoth they're becoming, so prices of frames is going to go up a tad. Buying last years models during the inevitable upcoming blow out last years bike sales are coming up....

thank you for the info......I have found several alternatives including NOS parts and updated 6 speed shifters. I really did not intend this to be a career change.
thanks again. mikecool

thank you for the info......I did do a little research and came up with just what I needed. Thanks again..mikecool