From my riding experience, with various mileage TWs, and from some research on the clutch "abruptness" and very short engage/disengage point, I don't think a new or aftermarket clutch will change the grabbiness that much.
I haven't read anything that indicates a much smoother or better feeling clutch in general happens with new or aftermarket clutch kits.
But the good new is that internal clutch mechanism is very much like most dirt bikes I've seen.
Metal and fibre clutch plates, metal clutch basket, springs for tension, throw-out rod in center. There are smaller covers which are a little easier to deal with. You can do it without draining the oil but I always suggest you do it while changing the oil anyways.
If it's not slipping in 4th or 5th I wouldn't worry about it.
Make sure the return spring is in the right spot and adjust the cable free-play to get the release point where you want on the lever and just use it.