1964 was the time in most jurisdictions when all the receptacles were becoming the grounded type. Do all those existing receptacles have the grounding prong hole?
Let's call them receptacles as not every outlet (by NEC definition) is a receptacle but every receptacle is an outlet. A receptacle is just one type of outlet.

Thanks for replying, bus_driver. Yes, they do have the grounding prong hole.

Carefully pull one out, if there is a ground (bare or green) wire connected to the third screw on the receptacle, your replacements should be straightforward (as depicted in your instructional material). There's a small chance someone put grounded receptacles in a not-properly-grounded box situation, but chances are if these things appear uniformly 50 years old no "harry homeowner" has been butchering the installation.

Thanks, ronnatalie. I was looking at a site that talks about converting a 2 prong outlet to a 3 prong, and the article mentioned what you just said -- that "Harry" could have incorrectly put in a newer 3 prong outlet in an old 2 prong box, so one should be on the look out for that. Just because the outlets are 3 prong on the outside, doesn't mean the innards are correct, so to speak.

Anything to be on guard for regarding light switches?

Older switches typically won't have ground screws so you may find the grounds cut too short to reach in boxes. You may have to pig tail a piece of longer wire on with a wirenut.

If there really is no ground in the swtich box, there is an exception that allows you to leave the switch ungrounded provided the cover plate is plastic.

First, get a plug-in ground tester and see if the outlets are properly grounded.

If they are, then replace them with 3-hole outlets.

It's really easy, providing you turn off the power first. Remove cover plate, remove screws, TAKE A PICTURE of how the wires are hooked up, loosen the wires and install them on the new outlet or switch just like they were on the old one.

A plug in tester will not tell you if the receptacles are properly grounded, just that the ground pin is connected to something at close to ground potential. We've already had a guy show up here in the past 30 days where some previous bonehead connected the ground to the neutral.

Ah well, maybe we'll just leave this to an electrician. The cleaning, priming, & painting are taking all our time as it is, and we've found a few weird things about some outlets, plus a ceiling fan that won't work. My son said he got shocked by one of the switches with a faceplate removed. Time to hire an expert.

Thanks to all who took the time to reply.

"If there really is no ground in the swtich box, there is an exception that allows you to leave the switch ungrounded provided the cover plate is plastic."

And plastic screws if I'm not mistaken.