I have a 90 suburban 4x4 1500 and I am installing a lift kit. I need to remove and replace the pitman arm attached to the driver side steering knuckle. it has 3 studs and nuts which hold it on. it looks like there are sleeves or inserts of somekind which ar down in around the studs. I need to know how to get it off.

Look at a Haynes manual or go to a library. Various parts stores lend tools you will need if you buy parts from them. You should have instructions with the lift kit as to exactly what you need to do. Lift kits change the wheel alignment and you will have to get a wheel alignment after changes are made.
Be very careful and follow the guidelines completely.