the transmission swap is not bad at all. If your car has little or no rust it is easier. I just dropped the catback, then drop the transmission. You will need a transmission adapter for your jack, and a few friends to help hold things up.
Working on jackstands might be a little tough for doing a transmission, if you have access to a lift that is a huge bonus.
It took my buddy about 2-3 hours to get the old trans out, and about 2-3 to get it back in, not including about an hour of wiring up the new transmission with the old electronics to make it work, and a couple phone calls to my 4r70w gurus. So, its a little shy of an all day job to get the whole deal finished.
A magnetic filter and a cooler are a must if you don't already have them installed.
If your car is not a 4.6 you won't be able to use the mark flywheel, or the converter, you will have to use a 3.8 tbird one.