Yep, I can help,

I have a similar 740. I also was not too thrilled with the factory
deck. I decided to replace it, and wound up removing the trim around
the infernal thing.  Theorettically, you should be able to insert a
LARGE paper clip or something in the access holes, but I had no luck
and found that if the knobs, EQ slider buttons etc. are removed, the
face plate comes right off, and removal is a snap. Do yourself a fovor
though and just buy, ( and yes, wait for delivery from Crutchfeld or
some similar source) a wiring harness kit and trim. There are some very
interesting and very SMALL wiring things going on there. Not the least
of which I can tell you, is the switched power supply, which is yet to
be figured out, and the fact that all of the speakers seem to share a
ground. I severed the factory harness, and wound up having to run
speaker cable to all four corners, and oh yeah, I still have to
manually shut off the stereo even after the key is switched off. Don't
get caught doing this procedure, it sucks. Save yourself a couple of
days, and just get the harness, Unless your time isn't worth much, In
which case would ya please let me know where the switched power is?

Best luck,
-Zeke-