It's pretty easy, though may be a little messy your first time. As they say, the oil really comes shooting out initially---be ready for that. I still spread newspaper under the catch pan and, these days, I typically don't get a drop on the driveway.
These will get you started:
http://www.986faq.com/7-0/oil.asp
http://www.pelicanparts.com/techarticles/box_oil_change/box_oil_change.htm
http://www.pedrosgarage.com/Site_3/Change_the_Oil_%26_Filter.html
http://986forum.com/forums/showthread.php?t=22045&highlight=oil+change
http://www.realtime.net/~rentner/Blog/B600322026/C339116892/E466985417/index.html
I didn't make a specialized oil catch arrangement like Pedro talks about (too much work
). I suppose it might be helpful, but I do fine without it.
Then there's the ramp vs jacking questions. I use the former, largely because they're easy and I already had made some out of 2x8s I had laying around. (I did that years ago, when I was only using them for a Toyota. These days I'd use 2x10s.) Here's a thread with a pic of what I use:
http://www.986forum.com/forums/showthread.php?t=19924
Since that pic, I have added bigger blocks of wood at the high end to prevent driving too far on (and off the end of) the ramp. I added them after the last time I used them, got in a hurry, and nearly did exactly that---would have been a bit of a disaster. The little strips that I used to depend on to prevent that were only 3/4" tall---you hardly feel them. The blocks on there now are about 2 1/2" tall---it would be pretty tough to drive over them.
As is suggested in the above links, you really want the Boxster level for draining the oil. I (and others) accomplish that by driving up my sloped driveway and then backing onto the ramps. Works great.