Avoid banging the shifter on anything if you can, a bitch to fix.
If you ride much trail on it, or develop a fondness for big drops
keep a close eye on the rear suspension linkages and the shock bearings. They like to walk loose, wallow out, and cost you a grand.
If I remember right, it has the air filter down through the seat? Tricky the first dozen times, and depending on how flexible or large your hand is, you may need someone smaller to thread in the bolt.
I recommend mounting up handgaurds, saves you a fortune in levers, though it isn't common in trials.
280 is a fine starter bike, and that is a good era. I don't see the point of underpowered bikes. You might as well learn clutch and throttle control to begin with, and the 280's and 300's are much more fun on the transport sections.
Congrats! Ride it like you stole it!, and buy a newer one when it blows. (I got a year out of my first used Gasser. The learning curve can be hard on equipment)