Easy is a relative term, with the engine in the car, it's not that difficult. For some of the guys here that have done this several times on the driveway, OR at the track, it's easy. For someone that has n't done it yet it could be a little daunting. But all said and done it's not that difficult of a task. You might need to remove the radiator just so you have a little bit better clearance.
For something like a project car that you're fixing up over time, you can pull the balancer measure it up and match it up with a replacement. A lot of times RockAuto will have these that are OEM and much better price than what you could get over the counter at your typical Auto parts.
If you want to improve on what you have, then after you take it off measured up, you can get with summit or jegs and see what they have available, and a lot of times they'll have the higher quality balancers with timing tape and all that already built into them.
Typically whenever I do a rebuild for somebody or restoration I'll use the timing tape, a lot of people don't like them because they do sometimes fall off over time. But I like the professional look of the balancer with a nice paint job and timing tape on it, that's just me.
You need a good quality half inch breaker bar, good quality half inch ratchet, good quality half inch torque wrench, and a puller and a press. If you have an O'Reilly's or AutoZone in your area you can rent that as a kit. Once the job is done you return the kit and you get your money back.
If you have the 305 or 350 with the probe pickup, you won't have the slot on the balancer where you need it to be for a timing tab. If that's what you have, you can still set it up properly cut a slot in the new balancer with a hacksaw just enough to make a groove lay some paint in that groove and then add a timing tab to your cover. This will make it easier when you get ready to time the engine.
The absolute most critical is prior to pulling the balancer off make sure you know where zero TDC is also pull the distributor cap to see where the rotor is pointing. If you don't do this your timing could be messed up when you get ready to start it, and it's going to be a little bit of an effort to get it re-timed. So just make sure your #1 piston is at TDC and your timing mark is at zero TDC. When you put it all back together and you should be fine.