How do I change a oil pump in my 98 Trooper, do.

OIL PUMP
Removal & Disassembly

Remove timing belt. See TIMING BELT under REMOVAL & INSTALLATION. Remove crankshaft sprocket from oil pump. Remove oil pan. See OIL PAN under REMOVAL & INSTALLATION. Remove oil strainer and oil pipe.
Remove oil cooler assembly. Remove oil pump bolts and oil pump. See Fig. 26. Remove pressure relief valve. Remove oil pump cover. Mark oil pump gears for reassembly reference. Remove oil pump gears. Remove oil seal from oil pump housing.

TIMING BELT
Removal
Disconnect negative battery cable. Remove air cleaner assembly. Remove upper fan shroud. Remove all accessory drive belts. Remove cooling fan assembly.
Remove cooling fan drive pulley assembly. Using Puller (J-8614-01), remove crankshaft pulley bolt and pulley. On SOHC, remove oil cooler hose from timing cover. On both engines, remove timing belt cover. Align all timing marks prior to belt removal. See Fig. 6 and Fig. 7 for SOHC models. Mark timing belt direction of rotation if reusing belt. Remove belt tensioner pusher and timing belt.
Installation (SOHC)
Ensuring all timing marks are aligned, install belt over one pulley at a time, starting at crankshaft sprocket and working counterclockwise. Belt should go over tensioner last. Secure belt at each pulley during installation with pinch clips. See Fig. 8.