How do you replace an oil pan for 2001 mitsubishi eclipse?

Assuming you're talking about the lower oil pan...it's very simple

1. Lift at least the passenger front side of the car using a jack, jack-stand, and blocks on the rear wheels

2. Drain the oil out of the pan by removing the drain plug (just like an oil change)

3. Remove all of the bolts on the outside edge of the oil pan (should be about 11)

4. After all of the bolts have been removed the oil pan is free to come off. It might still be stuck on and a few gentle taps with a rubber mallet with knock it loose. Be aware that there is still some oil inside the pan, so this step will be pretty messy

5. Clean the surface of the engine where the oil pan was mounted against

6. Take your new oil pan and place the gasket around the rim of the pan (if not using a gasket then put liquid gasket around the rim. This is important to ensure the pan doesn't leak)

7. Place the oil pan on the engine and bolt it back on. Start by tightening on bolt, then one as close to 180 degrees across from it. Repeat until all the bolts are tightened.

8. Fill the oil pan with new oil. You may also wish to remove and replace the oil filter.

9. If you used liquid gasket, give it a few hours to set (look at contained for a recommend amount of time to wait). If you used a rubber gasket, you don't need to wait.

10. Start the engine and check for leaks. If you notice any oil leaking from around the seal then turn the engine off, go back to step 2 and then repeat from there on. If you don't see any leaks, you are good to go.

The 3.0 engines you have to remove crossmembers remove transaxle rear bracket.remove starter and bell housing lower cover bolts.the 2.4 you have to remove front exhaust pipe and bell housing inspection cover then remove oil pan bolts.