With your good floor jack, put a piece of 2x4 or 3/4" plywood on it. About 6"-8" square. This is to keep the trans pan from getting mashed in one spot while it holds the weight.
Put the car on ramps or jack and support the car. Remove the three 15mm nuts holding the front mount to the subframe. The are in from underneath and don't support the mount, they simply hold it into the subframe. Bring the jack and and position it under the trans pan so that it spans and makes it to the edges then jack and watch things. You only want to remove the weight and see the mount move slightly at this point.
Remove the three 13mm bolts holding the mount to the trans casing. There is possibly one 18mm bolt holding the mount to the engine. I am pretty sure that came in later (around 96) though. Now the mount should be loose (might have a holder for trans lines (10mm). Wiggle and jack as needed to remove the mount. Slide new one in place and bolt to transmission, lower the studs into the subframe holes with the jack and remove the jack. Put the nuts back on and you are done.
00 Regal GS: All kinds of cool stuff.