Combining Dell N3000 Switch Stacks

I have a client that has two Dell N3000 stacks. One stack consists of 3 N3048's and the other of two N3048P's. I'd like to combine, and possibly remove one of the N3048 switches so that there are two POE and two non-POE, or something along those lines. Couple questions:

1. I undestand I can hot-add the swtiches from one of the existing stacks to the other. Am I to assume that I should reset the switches I'm adding into the other stack so that they aren't fighting on who is master with two different configs? Or do I need to shutdown the stacks and connect them together properly?
2. If I can combine them hot, I'm assuming that I can't just combine configs...I'll need to prep a config on the switches I'm adding to the stack that looks similar to the existing config but with the port ID's changed to match the new stack member ID?
3. Anything else I'm forgetting? The switches should be pretty darn similar in config such as routing, STP, etc but I'll check that out for sure.

Thanks!