If you can get a good deal on a used 550, I would NOT hesitate! That's how I got mine and Dillion will not care in the least if you're the second owner or the 50th. If something breaks, they'll fix it. Usually for free. If it doesn't run perfectly, ship it back to them and they'll make it 110% right. I've never dealt with a company that good (and generous) in the Customer service department.
If you're used to turning bolts and measuring things, this will be a piece of cake. And, like I said, you can break it down into the simplest possible steps -- even though the press can do everything at once -- while you're learning.
Conventional straight-walled pistol & revolver rounds are dead simple to reload anyway. When you get into loading for rifles you'll probably want a single-stage on the bench too, but let that come when you need it.
Last Saturday I loaded over 1,000 rds of handgun ammo on my 550B which involved changing dies and primer feed parts (large vs. small) twice. I probably wasn't actually at the press for more than 3 hours all told, though on lazy days like that I like to work in 15 - 30 min spurts and break it up with a little High Road surfing, playing with the kids, etc.
Lastly, if you have any questions or difficulties, with resources such as the folks at Dillon, and the folks here who contribute to our reloading forum, you'll never be too stuck. Help is pretty much instantly available 24/7.
(Oh, my chronograph is a Shooting Chrony Master Beta. They all work pretty well, but you really should have one. Even at newby stages and using the most tried-and-true loads ever -- the chronograph will teach you a lot about how cartridges work and how your different guns behave.)