Inherited Audi & Problems

[LRGreger@aol.com]

I inherited a 1988 80Q about 6 months ago.  Its my first Audi and its
wonderful.  I commute 80 miles daily in the LA area.  The car is smooth,
classy, and gets 30 mpg.  What more could one ask for, from a car.  There are
a few problems with the car though, and I'm looking for some advice.  The car
has 145,000 miles on the odometer.  It's burning about 1 qt of oil every 600
miles.  Is this something to worry about?  When should I get something done
and what?  Every once in a while some strange things happen, none of them
consistently.  The idle oscillates between 1k and 1.5k with a few second
period about one-third of the time.  The idle is too low and the engine dies
when it is cold (not too much of a problem in So. CA).  The engine pings
severely upon acceleration (very infrequent).  Any advice on what I can do
myself to remedy these annoyances?  There is one additional problem.  The
heater core started leaking and I disconnected and plugged the heater hoses
(again not a fatal flaw in So. CA).  How difficult is it to get to the heater
core to replace it.  I have one further question.  The belts, including
timing, were last changed about 100,000 miles ago.  Do they need replacing and
can I do the replacement myself?  I'm sorry for all the questions, but I
really love this car and have no experience with one.  Also, I'm afraid of the
$ of going to a dealer.

Thanks in advance for any advice provided.