>> I'm hoping at least some of this is relay related... and will be a
>> simple fix.

 First, i notice the radio is not being powered when the
>> ignition is off... it forgets its presets and everything.

You just need to wire the stereo into a source that's hot (12V) when the key
is off.  Make sure you're not picking a circuit that will overload with the
additional draw.  You stereo should also have a clock lead, which will
maintain your presets if you decide to have the stereo disabled when the key
is off.  If you choose that setup, run the clock lead to something that's
hot all the time, and the stereo power to something that turns off with the
key.

 Next, the
>> engine cooling fan does not come on at all despite the PO recently
>> replacing the thermo switch.

It doesn't come on until you get up around the middle or upper part of the
temp light.  If you're there, I'd check the switch with a multimeter to see
if it's engaging, i.e. putting out current.  I'd also try to put 12V to the
blower to see if you can get it to come on in isolation, so you can tell if
the fan is toast.

 The cruise control is dead too, but the
>> vacuum pump seems fine.

Not a cruise expert, but two easy things to check:  1) Is the unit actually
switched on at the lever in the cockpit (sounds stupid, but I've done it);
2) I have had the slider that hooks the vacuum ball to the throttle come
unsnapped

HTH,
bmc  :)