Back Wheel Smoking

[dereardo]

Hi there folks,
I took my bike out yesterday and after a mile of riding, I found that the back wheel was smoking and when I changed gears, if felt as if there was a drop in power and trouble getting up to speed.
The most recent history of this bike is that the time I took it out before that, it seemed like the choke was stuck open or that it was stuck in a high gear and continued to rev uncomfortably high the whole time I was riding it. A friend tinkered (I'm sorry I can't clarify what that means just yet) with it and it seemed fine for one short ride after that, and now there is a smoke fest happening.
I bought it at 12000 miles and now it has almost 19000 miles on it, and I haven't done any major work or had any major problems during those 7000 miles.

Does anyone have a place to start trouble shooting? My intuition is telling me its a clutch thing, but I'm not very mechanically inclined myself.

Thank you kindly,

dawn