I would pick up 4 quarts, put 3 in, and then keep checking the levels until it lines up on the dip stick. For me its about 3. 1/2 quarts, it's different for others.
as for getting to the filter, the honest best way to do it would be to pick up an oil filter wrench, get under the car, and turn it.
make sure that you lube up the new oil filter when you put it on.
It's easy once you start, but if you run into problems, make sure you ask for help.
goodluck