A clogged PCV Valve is known to cause rough idle. Verify if the valve has been changed recently.
The valve and grommet in my car were never changed and they broke into pieces and fell inside the valve cover when i tried to remove them. Took me an hour to fish out the pieces!
Seafoaming the valve train should help if there are deposits in the valve train. However, these deposits provide sealing in older engines and cleaning these deposits out may cause oil to leak through the valve seals, piston rings etc., causing oil consumption and smoke from the exhaust. I suppose this is a risk that you will have to take.
There is a Hirschmann brand antenna kit for $46 on ebay. I am planning to buy that for my car.
Does the car whine when the ac is turned off? If so, it is not the compressor. Try spraying plenty of wd40 into the compressor bearings. this should clear any deposits after the engine runs for a couple of minutes. Then use lubricating oil to lubricate the bearings as wd40 will evaporate after a while. A loud whine is not normal and must be diagnosed.
If the ac cools, but insufficiently, it could be that refrigerant is low. Check the pressure with a gauge and recharge if necessary. If the pressure is low then there is a leak somewhere.
The purchase price is a steal and even if you put in $3500 into the car, you are still below the blue book - for a car that is known to last for 300K miles!!