96 Plymouth Neon wiring: problem with speakers, blinkers, gauges

I have a 1996 Plymouth Neon (2.0L SOHC), somewhere between 120K-150K.
It's giving me some minor electrical trouble, and was hoping to get
some advice here. Here's a brief history:

2003 and befo
- when applying brakes, the left blinker lights up (front, back, and
console). Giggling the turn signal switch helps. This is still going
on today.

2004

-the dash gauges started getting wonky. Now, the speedometer registers
the correct speed about 25% of the time. Occasionally, none of the
gauges work at all.

- right rear blinker/bright light was out. I went to put a new bulb in
and found that part of the socket had melted and covered one of the
contact wires. I popped the wire over the melted plastic and the
original bulb worked fine.

2005

-the passenger side door was hit while the car was parked on the
street. Right after the frame shop put a new old door on, I noticed
that the front speakers did not work when the passenger door was
closed. They worked fine when open. The shop said there's something
wrong in the wiring under the console. Now, the front speakers don't
work at all.

Do any of the above symptoms seem to be related? I've read a little
about bad solder joints on these early models, and thought maybe that
was the problem. If that's the case, I'm pretty comfortable with a
soldering iron and could probably do myself. I just need to find out
where the problem actual lies. Where should I look? Would I have to
pull the dash off? This is an older car, and I don't necessarily want
to spend a lot on "optional" repairs (after all, I have to save up to
repair the leaky head gasket!).

Thanks for any advice.

Joseph