First off, unless it's leaking, (and I've never seen a one piece leak yet), I wouldn't replace it.
Unless of course, (flame suit on), you're going thru the motor, and/or freshening it up/reasealing everything.
There are special tools for removal/install, but you can do it fairly easy (insert patience here). Biggest concern is scratching the crank sealing surface, and the block sealing surface. I've seen lots of people literally dig with gnarly picks, get the seal out and in, but they've trashed the surfaces so bad that it had to be 'rigged/sometimes remachined to repair it properly. No chit. I can only assume you have the engine out of the car, and/or transmission/flexplate, all that removed, with lots of access to the seal, right? Sometimes drilling a couple 1/8" holes in the middle of the seal, then inserting a screw, then prying those out, (being especially careful how deep, and angles that you drill), and pull the seal out that way.
For installing, cleanliness is the gig. A little lube/oil on the inner seal, and on the crank, and I like to put a little sealer on the outside/block area), and make sure as you're tapping it in, (with a light hammer), or better yet the special tool for it), being careful not to cock it and tweak the seal.
Again, just be careful, take your time, and don't let it get the best of you.
If you can get at it, and have a fair amount of tools, it's a fairy easy job. It's also just as easy to screw it up, trying shortcuts/hack, etc.
Good luck, and have fun.