simple question

get up under the car remove the drain plug, let all the oil drain out then replace drain plug, the remove oil filter, smear a little bit of the old oil around the seal on the new oil filter and screw it back on, then get back out from under the car and fill the motor up with oil

Pretty much what he said. Except, Check to make sure the old gasket is still on the old filter. And don't use fram oil filters. They are junk. Use a motorcraft or puralator(same filters in differant package. AND USE JACK STANDS!!!!!!! NEVER GET UNDER A CAR WITHOUT THEM!

Wix filters are also a preferred brand.

No one mentioned the other little gotcha of changing the oil in a Fox3/SN95 5.0 Mustang.....your oil pan has two drain plugs. One is for the small front sump, the other for the larger rear sump. You need to drain both. The engine takes five quarts with a filter change. If it reads above the full mark with the proper 5 quarts in it(as many do), then the dipstick is wrong. Take note of the "actual" full mark and go by that instead.

+1 on the double drain tip. first time i changed my oil i was like WTF!!! only about a litre came out. took me damn near half an hour to figure out why. these cars have 2 oil drains because of the design of the oil pan. make sure to drain both. i like to jack the front end of the car up a bit because i can't really fit under there too good if i don't. and i'm only 160lbs... makes it easier. then take off the filter. make sure you have the old rubber gasket from you old filter. run a little oil over the new one so it wont stick for when you change it again. put the drain bolts back in, and filler up with oil. not sure if you use Litres, but i think it takes 4.7L of oil. i assume you know you'll need stuff like a drain pan, funnel, container for old oil (i usually just use the big jugs of new oil so i use that once i'm done filling the oil, after putting what's left over into a small 1L container) and a way to dispose of it, and maybe some brake cleaner to clean the spilled oil off the underside of your car.