1999 Dodge Caravan how do you change the water pump and should I change the timing belt at the same time

For what liter engine?

TIMING BELT
Removal
Raise vehicle on hoist and remove right front wheel. Remove right inner splash panel. Remove accessory drive belts. Remove crankshaft vibration damper.
Remove generator drive belt idler pulley. Remove lower timing belt cover.
Remove right engine support assembly vertical bolts from bottom of frame rail (timing belt end of engine).
Lower vehicle. Remove upper timing belt cover. Place floor jack under vehicle to support weight of engine and transaxle assembly. Remove 3 bolts attaching engine mount assembly to engine bracket.
Move A/C drier aside. Remove coolant reservoir tank. Remove right engine mount. Remove 3 bolts attaching engine mount bracket to engine block.
CAUTION:Align timing marks by rotating crankshaft only. Do not rotate camshaft after timing belt is removed, or engine damage may result.

Rotate crankshaft clockwise to align timing marks on camshafts and oil pump housing. See Fig. 1.
CAUTION:Crankshaft sprocket mark must be located on trailing edge of sprocket tooth. Failure to align trailing edge of sprocket tooth with oil pump housing mark will cause camshaft marks to be misaligned.

On models equipped with hydraulic tensioner, remove hydraulic tensioner bolts and remove tensioner. Place hydraulic tensioner in vise, and SLOWLY compress tensioner plunger. Align the holes in the tensioner body and plunger, and insert a pin through the body and plunger to lock the plunger in place. Skip next step.
On models with a mechanical timing belt tensioner, insert a 6-mm Allen wrench into tensioner. Insert long end of 3-mm Allen wrench into pin hole on front of tensioner. While rotating the tensioner counterclockwise, push in lightly on the 3-mm Allen wrench until it can be pushed into locking hole. See Fig. 2.
On all models, if reusing old timing belt, mark belt with arrow to indicate original direction of rotation. Remove timing belt.

Removal
Raise vehicle on hoist. Remove right inner splash shield. Remove accessory drive belts and P/S pump. Drain cooling system. Support engine from bottom and remove right engine support. Remove P/S pump bracket bolts and set pump and bracket assembly aside (P/S lines need not be disconnected).
Remove right engine mount bracket. Remove timing belt. See TIMING BELT. Remove inner timing belt cover. Remove water pump-to-engine attaching screws. Remove water pump.