yes you can make the shee a trail bike. get a 2 into 1 pipe and a 2 into 1 carb, bump up the compression a little, and shee will be good to go. just rember to point that banshee were you want it to go and hang on, white knuckle riding past the trees is a rush!!
eather bike will be a good choice, they are both easy to work on, and parts are easy to come by.