I'm trying to get my Multiprise 3000 up and running. Is there something like this for S/390?

Search that Redbooks site for 'abcs of systems programming'. There's a 5-volume set from 2000 that covers S/390 and OS/390.

Also check out the OS/390 ADCD Redbook:

https://www.redbooks.ibm.com/redbooks/pdfs/sg246204.pdf

Which I found pretty helpful for finding my way around. (I see from the cover that it includes MP3000 info!)

Edit: Have you seen this? (I think this guy hangs out on HN)

ftp://ps-2.kev009.com/incoming/timc/PDFS/IBM/S370%20&%20S390/MultiPrise%203000

He does. He's been a great help as I try to piece together enough stuff to function as a system element. And thank you for that redbook link; I have a load of stuff, but somehow missed that one. Thanks!

Can Hercules run MP3000?

The MP3000 (Multiprise 3000) is the smallest mainframe IBM ever made, weighing in at only about 300 lbs. Using the vanilla Hercules, it can be MIPS limited to act mostly like a MP3000 System/390 machine and run the same OSes.