Toronado.org

I've only done it with the engine out of the car! It's the only way I've been able to get a perfect seal... However, I have heard from others that they do one or a combination of things: * Unbolt the oil pan until it can drop enough to get the front cover back on and properly seal. I worry about warping the pan, the rear seal and getting the pan itself sealed back up completely.
* Remove the front mount bolts, lift the motor a bit from above (very carefully here so as not the damage the rear mounts and final drive parts) and lowering the oil pan.

I'm sure others have better information here. So, I'll leave it at that!