Hey all. I have a 70's era Snapper 3080. Ran great for the last two months - as long as I've had it. Now it will not drive in any gear. The clutch mechanism seems to be fine - I can move it into all gears and watch the parts move from underneath, as they should. But when I start it and put it into gear, it doesn't move. This happened suddenly, on the last mow, coming out of reverse. Thinking about opening up the transmission to see what's in there. Any advice/suggestions for a novice before I open her up?