Presses--Questions
Not dumb questions. You need to know before you take the plunge. It has been said that there are no dumb questions because if it occurs to you, it is an intelligent question. (Unless you were--grrr--not listening or something.)
And dumb questions, if they exist, are easier to handle than dumb mistakes.
Congrats on deciding you need to reload. You'll never be the same, but you'll like the difference. On to your questions:
The standard advice is almost always to get a single stage press first, and learn the steps on it. There are several advantages: You have only one thing going on at a time to watch. You can get good at one stage before going on to the next. If you should happen to decide you hate handloading and want to get out, you are in for less money, therefore less loss. If you go ga-ga for handloading you might upgrade to a progressive, but you'll always be able to use your single-stage for short runs, and for load development.
A progressive does everything all at once, producing one finished cartridge with each pull of the handle, and advancing the cartridges through the process. Those who shoot A LOT usually get a progressive--competitive pistol shooters for example.
If you get a progressive get at least a 4 holer--the extra hole(s) are useful for powder measure, powder charge checker, etc.
Dies are almost completely interchangeable between machines. Some dies work better with progressives--Dillon's for example, have big tapered openings so the cases go in easier. One machine will use another manufacturer's dies w/o spitting up. The exception is the Dillon Square Deal B press, which uses its own proprietary dies. That's the only one I know of like that.
Lee presses are cheaper because they are made cheaper, so they can be sold cheaper. Now, that may or may not be a disadvantage. A lighter cheaper press can do almost everything the sturdiest can do. But if you are sizing some really tough cases, for example, you'll be glad you have an RCBS Rockchucker or a Lyman Orange Crusher and not the Lee. Or if you crank out hundreds of rounds. (Of course, if you crank out thousands of rounds, you should be on a progressive!)
The standard advice is to go ahead and spend the extra and get the Rock Chucker--it'll outlast you, and your son, and still be in perfect alignment. That's what I'd do were I you, but it's your Mastercard, not mine, so you make the call.
Now, before you jump in to reloading with both feet, may I suggest a purchase first:
The ABC's of Reloading published by Krause
www.Krause.com which is THE BEST primer IMHO, and will answer questions like these for you. It's also faster than using the I'net one question at a time. They just came out with a new updated edition. Well worth yr. hard-earned $$.
Hope this helps!