Is this safe to do, any things to watch out for, be aware of? Potential damage?

I know with Seafoam its been known to occasionally kill weak spark plugs and possibly upset your O2. I didn't have any of these issues when I did it, but I changed them out just as a precaution.

Search for this, lots of info here...

Big red thing? "Engine washes" have become popular among shops, although their benefits seem to be minimal over conventional methods.

It isn't supposed to damage anything.

You may need new plugs when done.

You MUST change your oil when you're doing it through the vacuum/intake ducts/cyl cleaning. And you'll pretty much need new plugs when you're done, and It'll knock the deposits out, and they'll land on the first few screens in your catalytic converter.

Doing this on a high mileage cat, can clog up everything that hasn't been clogged yet...

It will "restore" lost mileage due to ineffecient burn in the cyl from hot spots, not just give you more mileage.