5KCSQ idle and HVAC problems

[paanta at splatterfish.com]

My (just purchased) '88 5KCSQ is having idle problems.  The car
needs the gas
pedal depressed to start, and once it's started, it won't idle.  The idle
gradually
decreases until the car dies.  The car runs just fine, though, making
good smooth
power.  After its been running for a while, it will idle, although not
spectacularly well.
Sometimes it'll get down to about 500 rpm and threaten to die.

Any likely culprits?  I know the multi-function sensor is burned out,
because the
dashboard coolant display doesn't work.  Could this be the cause of
this sort of
behavior?  How about a vacuum leak?

The blower is stuck on the second setting.  Other than that, it works
well.  I'm told I
can buy a chip from Blau that will fix this problem?

In addition to the idle and HVAC problems, the gas guage doesn't
work.  It's stuck on
E, and the low gas warning lamp is on.  What's a likely culprit of this?
I don't have a
bentley yet, and I'm hoping to get some of these things squared
away by this
weekend, so any help would be appreciated.

Last, but not least, the A/C compressor seems seized.  Does anyone
have a
(working) spare sitting around that they'd sell me?

  -Pat