Hey Steve,
I have a 7100/66 that I bought new in about 1994(?). In around 2002,
the monitor went dead, and I replaced it with a PC-type monitor,
Hitachi v700, which has much higher resolution than the original
did. To use the V700 with the HPV card that came with my 7100, I
needed a special adapter connector that had a row of DIP switches,
which were settable and accessible on the case of the adapter. The
dip switches had to be set to a specific configuration, and I
verified that the monitor would not work unless the DIPs were set
right. I can get you more info if you need it but try the PRAM first
(mine goes bad every 2 or 3 years).
As for your other questions, my machine did very nicely with an
accelerator card from Newer technologies. It runs much faster and
can handle system 9 quite well. It even runs web browsers, but there
are some issues transferring data to system X machines. If you get
an accelerator you should make sure its the one with the video pass-
thru.
G.G. McGrane