So yeah, it's not really "hunting" per se...More like plinking at live animals. And you honestly don't need a fancy optic. I used to kill slews of them with a Walmart blister-pack Tasco 3-9 on a 10/22. I don't do it anymore because these days I'm not really into killing things for entertainment. It damages my karma and I prefer to just leave them to their business. But I suppose it is fun and is worth experiencing so you do you. Not like they're endangered or anything.

Anyway, the Trijicon you have now will be fine. As long as the glass is clear and the zoom is reasonable enough for you to see a coke-bottle sized thing at 400yds well enough to provide it a clean death, you'll be fine. I don't think you need FFP for prairie dogs, but if you find your multi-purpose unicorn optic, having FFP won't hurt you. You can go as fancy as you want. I know guys running $2k Mk5 HDs and $4k ZCOs on their prairie dog rifles. A suppressor can be helpful if you have access. After a while of shooting, they'll scram down their holes...Less noise stretches out the session.

Main thing is to take sunscreen and lots of water 'cause you'll be sitting in the sun all day.