A few more questions about Linux LPARs, HMCs and other items

Pondering starting down the LPAR road now but I have a few conceptual things I need to sort out first.  I have had a couple of LPAR experiences in the past but not with an HMC so I am a little uncertain on how to proceed.  A LONG time ago I used VPM to create a Linux partition.  As I remember it, it was a little un-intuitive but it worked.  On my JS12 blade, it was a whole lot easier.  I used the IVM in VIOS to carve up the available disk and CPU's.   With the vHMC, I really haven't used it to assign anything.  The 9009 was installed using the console so I didn't have to decide how much disk, memory, etc was allocated to IBM i. So, like I said, I just need to get my feet on the ground with concepts.

Some of the stuff I have read seemed more like using a VPM and yet there are references that the HMC makes its more like the IVM.  So, I'll start with a few questions:

1) The 9009-41A I have has 4 cores, three of which are idle.  Are those cores available for non-IBM i workloads?  Do I have to use the $PEND MONEY command to activate them?

2) Was there an essential "first step" that I should have taken if I was planning to run non-IBM i workloads along side the IBM i one?  Something tells me that everything should be virtualized to be able to "slice and dice" the 9009 to different workloads.  If so, does VIOS need to be the underlying OS with everything on top of that?

Several folks suggested online resources to create the LPAR. There just seems to be a few different approaches to how to handle the hardware side of things.  I can see where I could "steal" existing resources from the IBM i side, but my hope was that I could utilize the unused cores in in the Power9 and also, if necessary, allocate disk to the other partitions.  Not seeing a way to do that.

I saw posts from Michael Quigley, Patrik Schindler, Steve Pitcher, and Jack Kingsley that filled in bits and pieces for Michael when he was contemplating his Linux LPAR but it didn't completely fill in the blanks for me.  Answers to the first two questions will determine my next step (and questions).