your going to be doing some heavy maintenance soon, but it is all normal. I
bought a 2000 for my daughter, I have a 2001.
Here goes;
at 60,000 you MUST have the timing belt changed,
plus you might was well replace the roller tensioners at the same time,
comes as a kit. Change the water pump while that is apart, as you are
right next to it. while it's apart, plugs, and fuel filter, and ignition
wires and cap and rotor. Probabily a new set of belts too, as you have to
take the old ones off to get to the timing cover.  Drop the tranny fluid,
and put in a new transmission filter and gasket set. Change the transaxle
oil, replace the front axle seals, and probabbily he 4wd seals. Cost me a
shade over $700 with an $80 an hour labor rate (NY rates). I provided the
timing belt kit ($102).Took a day. Then you are good for another 60,000
miles, if you change the oil every 3000 miles. As for the stereo, simple.
pry open the black bezel, remove the 4 screws that hold the radio, it
comes out  with the black compartment bolted to it.
put the new one in the same place, and put it back. I put a Kenwood in
hers. Pep Boys has a plug adapter that just plugs in the back and into the
Kia harness. plus you will need a Motorola to mini motorola antenna
adapter, again I found it for $4 at pep boys, but if you need another
source, contact me. I have a few of them. If it's not a DIN standard
radio/cd player, again email  me and I'll send you the name of a
wholesaller who stocks a Kia adapter plate for under $20.
The windows are usually the lift arm has come off the track, of the motor
has burnt out from being jammed. see if you can pull it up by hand and
silicone the track, you might be able to recover the motor.
Squeeky belt will be fixed with the above, just need tightening.