To do the clutch you need to pull the transmission. The engine stays in the frame. Being a new owner in there for the first time figure a long day of about 8 hours to do the job. There are several screws and bolts that need to be replaced along with the clutch plate. Total cost should be under $200 for parts. eBay is your friend for clutch discs.
There are a couple recent threads around here about replacing the friction disc.
It would be a good time to get in and do a few maintenance jobs as well. Clutch spline lube, o-ring, drive shaft and swing arm bearing lube as well. You'll have a like new drive train.
As far as engine life, if the oil and coolant are changed at the proper intervals, there is no reason not to expect at least 200,000 miles from that engine.