Random post, I know, but I often find these posts useful, especially when I was a lurker. I recently installed an epoxy floor on my garage, and if there's anyone contemplating doing this, I offer this advice. First, you can do it. I'm a greenhorn with home improvements and all things like this, but if you prepare well, you can do it. Also:

I highly recommend Spartan Epoxies. Industrial grade epoxy, not the Rustoleum junk you buy at Home Depot. This is great stuff. They have instructional videos and their customer service is top notch. Everyone you talk to on the phone is eager to help and has years of experience. No customer service people on a script.

Prep the floor. You need to diamond grind it just like you'd sand wood before staining with really no exceptions. I went cheap and grinded my entire 3 car garage with a 7" grinder. Saved a ton of money over a big machine, but it took way longer and using an angle grinder makes it much more likely to grind too hard or unevenly.

Make sure you have all the stuff you need well before you embark. I cut it too close and was scrambling, but I got it.

I went the extra mile and filled in the spacer joints with polyurea for a seamless look. Looks great, a TON of work, though.

Have a friend help. Very important.

Here's a short video of the final result: https://vimeo.com/470764308