It isn't hard to do. There are several bolts that hold it on. The worst part is when removing it, the fluid will fly everywhere if you're not careful. Just purchase a new filter and gasket at the local parts store so you can replace the filter too (easy to do). WHen you remove the pan, loosten all bolts except 3 that are side by side. After the rest are out, begin loostenrtg the three slowly so the pan starts to open on the opposite end. That way, the fluid will pour out of one side rather than everywhere. Once it is drained, remove and clean the pan, remove all old gasket from the pan and trans, replace the filter that will be right there, and reverse the sequence. Make sure not to over tighten the bolts or you will end up with a new leak.
As far as the number of quarts of ATF, first make sure to get the correct type (I BELIEVE it is ATF+4) it will say it on the dipstick. Start with around 3.5 to 4 quarts. Start the engine, run the shifter through all gears a few times and allow the vehicle to warm up. Then check the level and fill it as necessary. I think 4 is going to do it, but it may be a little less or more.