Re: Romex, GFCI & 3 prong outlets - good sign?
The presence of three-prong outlets is no guarantee that the outlets have been properly grounded. A previous owner may have replaced two-prong with three-prong simply for convenience, without grounding them.
Another possibility is that the ground was "bootlegged" to the neutral wire: if the building wire does not have a separate ground, sometimes people will just run a jumper between the grounding screw and the neutral wire. This will fool a "3-light" tester into showing a correctly wired outlet. Under certain conditions this can be dangerous, and it can render surge protectors and line noise filters ineffective.
Where it gets especially dicey is when a bootleg ground is installed on an outlet that has been wired with reverse polarity. (Search the Internet for "reverse polarity bootleg ground") This condition will also cause a 3-light tester or even a multimeter to show a correctly wired outlet, when in fact a grounded device plugged into that outlet will become electrically hot! That is a potentially deadly condition.
The only way to really know for sure is to open up each electrical device for inspection, and meter each conductor against a known good ground -- such as in an extension cord plugged into a good outlet.
But you might be lucky; everything might be just fine. I only want to alert you to some things to watch out for.
The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.