*edit-while you are there, might want to replace the oil pump also.
REMOVAL & INSTALLATION
Fig. Fig. 1: 4.9L engine oil pan installation
1. Drain the crankcase.
2. Drain the cooling system.
3. On 1987-93 models, remove the upper intake manifold and throttle body (see ).
4. Remove the starter.
5. Remove the engine front support insulator to support bracket nuts and washers on both supports. Raise the front of the engine with a transmission jack and wood block and place 1 in. (25mm) thick wood blocks between the front support insulators and support brackets. Lower the engine and remove the transmission jack.
6. Remove the oil pan attaching bolts and lower the pan to the crossmember. Remove the two oil pump inlet tube and screw assembly bolts and drop the assembly in the pan. Remove the oil pan. Remove the oil pump inlet tube attaching bolts. Remove the inlet tube and screen assembly from the oil pump and leave it in the bottom of the oil pan. Remove the oil pan gaskets. Remove the inlet tube and screen from the oil pan.
7. Clean the gasket surfaces of the oil pump, oil pan and cylinder block. Remove the rear main bearing cap to oil pan seal and cylinder front cover to oil pan seal. Clean the seal grooves.
8. Apply oil-resistant sealer in the cavities between the bearing cap and cylinder block. Install a new seal in the rear main bearing cap and apply a bead of oil-resistant sealer to the tapered ends of the seal.
9. Install new side gaskets on the oil pan with oil-resistant sealer. Position a new oil pan to cylinder front cover seal on the oil pan.
10. Clean the inlet tube and screen assembly and place it in the oil pan.
11. Position the oil pan under the engine. Install the inlet tube and screen assembly on the oil pump with a new gasket. Tighten the screws to 5-7 ft. lbs. (7-9 Nm). Position the oil pan against the cylinder block and install the attaching bolts. Tighten the bolts in sequence to 10-12 ft. lbs. (13-16 Nm).
12. Raise the engine with a transmission jack and remove the wood blocks from the engine front supports. Lower the engine until the front support insulators are positioned on the support brackets. Install the washers and nuts on the insulator studs and tighten the nuts.
13. Install the starter and connect the starter cable.
14. Install the intake manifold and throttle body, if removed.
15. Fill the crankcase and cooling system.
16. Start the engine and check for coolant and oil leaks.