It's kinda hard to make an accurate diagnosis with the information given, but let me tell you this:
1) A compression test would be a guaranteed way to determine if your engine needs rings or not. If the compression is low, you should squirt some lightwieght oil into the cylinder (which will temporarily coat the pistons and rings), then you perform another compression test and if the numbers go up, your rings are worn. A compression gauge is pretty cheap (certainly one could be bought new for less then $50) and pretty easy to use. You simply remove all the spark plugs and disable the cars fuel system (no sense in having fuel spraying around, just pull the fuse for the fuel pump). You screw the compression gauge into one cylinder and crank for a few seconds. The guage will record the pressure achieve by that one cylinder it is screwed into. Repeat for all cylinders involved and if any are low then use oil as described above to determine if the problem is on the 'top end' or in the 'bottom end' (Valves/Guides/Head Gasket or Pistons/Cylinders/Rings).
2) A quick and easy way to determine if your Valve stem seals are leaking is this: place the shift selector in first gear, drive up to a decent rate of speed (no need to go really fast) and let off the throttle while letting the engine slow the car down (you will need to be in first gear in an Automatic trans.), then accelerate again while looking in your rearview mirror. Look for a puff of smoke. What that test does is starve the engine for air (the throttle is closed) forcing a high vacuum situation. The engine will suck air in from wherever possible and if your valve stems/seals are bad it will carry in oil with the air. When you accelerate again the oil gets burned off and gives a tell-tale puff of smoke from the exhaust.
3) It would be easier for you to get a book with pictures from the library (or perhaps Google) then for me to try and describe what a oil fouled spark plug looks like. If your plugs are black (like you said) your problem could be too much fuel which could be caused by a clogged throttle body. That would also give a hesitation and perhaps smoke when accelerating from a stop. To put it simply, when your engine is idling the throttle 'butterfly' is closed. Air needs to come in from somewhere and if the passage is clogged up with carbon (as tends to happen, even more so with older cars) then the air fuel ratio gets upset and the car runs rich (too much fuel). The plugs get 'wet' or 'fuel soaked' and when you accelerate the engine hesitates as the excess fuel is burned off. Some cars have a hole in the butterfly, some keep the butterfly open a little bit, and others use a 'idle motor' which opens and closes an orafice to allow more or less air in depending on the target idle.
4) I should mention that you really should check to be sure that your plugs are the right numbers and are gapped properly. Different spark plugs have different 'heat' ratings. If your plugs are too 'cold' then you could they could be discolored like you described. Also, if someone dropped the box of plugs and the air gap got closed in a bit, the spark might not be big enough to burn off all the fuel/oil which could give the conditions you described. I doubt it, but I prefer to start with the basics when guessing at a car I can't check myself.
I realize that this reply is rather long, but I tried to give a relatively easy way to diagnose your problem. I haven't seen anyone else post a way to diagnose your condition. I try not to guess, I prefer to diagnose. Post back with some results of what you find or PM me for more information or things to check.
Personnaly, I have a 1983 Volve 240 with over 265k on the odometer. I should mention that sometimes the odometer sticks, so the car most certainly has more mileage on it. Also I should say that the speedometer and odometer stopped working recently, it's probably just a speedometer cable and I will get to it sooner or later. My 83 runs like a champ and I will only get rid of it if it needs a large infusion of cash or if I find a great price on a better car. I drive into NYC everyday and NY roads are pretty rough. No sense in replacing this car if I don't need to. It doesn't burn any oil and has E.F.I. (no carb), 4 wheel disc brakes (4 piston calipers in front, 2 pistons in the rear), Overdrive Auto trans, etc...). Perhaps ABS brakes would be nice, but I don't miss them much.
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