I guess I will add my opinion here as well. I would flush with seafoam, I have found it to be a great engine flush, along with intake/fuel injector cleaner. I would also do as instructed on the back of the can for the flush ( it's been awhile since I have done it) you can pick seamfoam up at walmart, around $8 a can, you will have enough to treat the oil once, and then the fuel system depending on how you want to attack the fuel system..which would not be a bad idea being it has set so long. One thing not mentioned here, and what I have found to be the best defense, and cure for sludge, old gas gum etc is drive the stink out of hat car, rack up some miles, good long miles, a operating engine at operating temperature at a good long drive (50 miles are so to get started) will do that engine great, combine that with a oil like PP, Maxlife, etc etc and you have a good chance that if any sludge did form you will be cleaning it out, also while doing so good fresh gas will clean up the fuel system. I'm half way for, and half way against all the additive junk out on the market, I have seen what they do in general they take money from your wallet, and add deposits on your plugs (in the case of injector cleaners etc) good, clean fresh gas is all that is needed to keep your fuel system in tip top shape, I'm not so sure about the oil additives, however if it's anything like the gas additives... see above.
One place solvents do help is the intake around egr valves etc where carbon does build up, and where the smog system is recirculating that nice gunk around, in this area I have seen benefits from the many solvents (seafoam being one of the best in this case, also B-12 chemtool)
Hope I didn't cross over any lines here, however this is real world hands on, no frills, no lies, just facts experience of mine. It's no wonder why the car manufactures do not recommend any additives to or engine system.
