mehavey's advice is good. Learning on a progressive is kind of like learning to walk wearing roller skates. It can be done, but it is a lot easier if you start out wearing regular shoes.
You can do it. But it is easier to do if you pretend your Pro-1000 is a single-stage for a while.
I never did get comfortable with trying to watch my Pro-1000 presses performing three operations at once. Trying to keep track of multiple simultaneous events was just beyond my powers of observation.
But all of that is beside the point.
First, if your powder measure is an auto-disk (a likely assumption), and you have the spring and "F" lever to substitute for the chain and "T" lever, you can operate satisfactorily. I did on my Pro-1000s for three decades before I even knew there was a "T" lever and chain.
Second, the Lee Pro Auto-disk is designed to work in conjunction with the Lee Powder-through and expansion die. As IllinoisCoyoteHunter and abelacres have intimated, I don't think the Lee Auto-Disk powder measure can work with the RCBS Dies.
The salesperson who told you the Lee Powder Measure would work on a Lee Press is (technically, and in a limited sense) correct. The Lee Auto-Disk will work on virtually ANY press. However, he completely missed the point. As far as I know, the Lee Autodisk will ONLY work with Lee Dies. It does not matter what press they are mounted in. The measure actually mounts on the die. Only the chain (if you use it) connects to any part of the press.
I was once sold (against my will-they changed my order without checking with me) a standard Auto-disk because the salesman thought the Pro-autodisk would not work with my Turret press. Wrong. Just because a guy works in sales for a company does not mean he knows diddly about the product.
One of the nice things (for me, at least) about Lee is that they provide the appropriate shellholder with every set of dies. No other die maker does that. It actually makes sense, since many shell holders fit different cartridges. If you load that family of cartridges, you just wind up with extra shellholders, or if you use a progressive (as you do) the single shell holder Lee provides free is of no use at all. For your progressive you will need the shell plate (shell holder) for the 38 Special. The 9mm plate will not work, as you have discovered.
Many loaders not only buy the shell holder for their different cartridges, but buy the entire carrier (primer feed, carrier, shell plate, the whole assembly) to make caliber changes more convenient.
Good Luck
Lost Sheep