loadmaster

Have had truck since new. 125.000 miles 4.2 motor stick shift 4WD. Regular cab and box. I first noticed the problem a week ago, it first showed up while warming the truck up in the driveway the speed-o meter would would bounce up to 100 MPH and the milage would advance this would continue everytime that I gave it gas in nautral until I drove it about a mile. Now today, I noticed that speed-0-meter was working fine but while driving on the freeway, and accelating, the tach would go up but not the speed then the tach would move around 200-500 rpm and then settle down until I gave it gas it again. While climbing a hill I do not notice any slipping

I am thinking it is time for a new clutch. What kind of job am I looking at? I am not new to car repairs just never a clutch with 4WD. Thanks