So I got a message from a buddy. He bought a house from the 1880's, and takes possession of it next week. He want's to change out all the ungrounded recp's. I was worried I would have to rewire his whole damn house and did a quick forum search and saw that I can replace them with a properly labeled GFCI. The GFCI will still function properly correct?
A house built in the 1880s probably didn't get any electrical at that time. The electrical system was installed at a latter date. The thing to figure out is when and how the electrical system was installed and maintained.
A friend of mine bought an old house built around 1900 and wired around 1930-1940 and rigged all to hell after that. If you pulled all the bad wiring there wouldn't have been any left.
The first thing to do is inspect the wiring to see if it's safe. A GFCI will keep your friend from getting electrocuted but may not protect him from burning to death and even an arc fault may not prevent this.
Go in the attic and crawl space or basement and check the condition of the wiring. It may be rat chewed and spliced with anything and everything imaginable ( it happens). Or it may be in pretty good shape.