I have a 2002 Monte Carlo SS with a 3.8 and I was wondering if it would be possible to drop the oil pan to replace the gasket in my garage with just a floor jack. And is it necessary to use an engine hoist or something to hold the engine in place or would it be possible without?

 

Going by the book, replacement of the pan gasket requires removal of the oil pan which requires removal of the sub-frame (AKA-engine cradle), so you need to support the engine from above with a engine support bar or hoist.
With that being said...I have heard it's possible to replace the oil pan gasket without completely removing the pan, but that member also commented that it was a real PIB.