> 1. How do I tell if I have a PMMU installed, or not.

I think there are utilities which tell you your system configuration
in detail, but I don't even know the names.  I'll let other people
answer this.  However, as far as I can tell from the boot message,
your Mac II doesn't seem to have one.

> 2. How do I get a M68851 if I don't have one installed. I have heard they 
> are scarce...

I know there is at least one place who carries the chip for about $90.
I found their ad in Macworld.

Alternatively, you can get the same functionality by installing a
68030 accelerator in your Mac II since 68030 has a built-in PMMU with
which NetBSD/mac68k works just fine.  I'm running NetBSD/mac68k on an
SE/30 beefed up (a bit ;-) by DayStar PowerCache (68030+68882@40MHz)
with the secondary cache disabled (NetBSD doesn't boot with the
secondary cache enabled), so I don't think you should have any problem
with a 33-40MHz 68030 accelerator with no secondary cache on a Mac II.

ken