Toyota Repair: Shortly after a tuneup a couple..., head gasket problems, toyota 4runner

Question
Shortly after a tuneup a couple of months ago, my 1993 Toyota 4Runner began running rough.  It ran smoothly before the tuneup and periodically runs smoothly, although mostly runs rough.  It has 156,000 miles on it, about 90% of which is high speed freeway driving, since I do a lot of long distance driving in my work. The dealer tried to convince me to do an engine rebuild, but I declined at this time.  I like the car, partly because it is a stick shift, but mostly it never gave any trouble until the tuneup.  I always get oil changes after 3,000 to 5,000 miles and always got the recomended dealer service every 15,000 miles.  Could a bad spark plug be the cause?  

Answer
Yes it could be a bad spark plug along with a number of other reasons:
Spark plug wires
Distributor cap(possibly cracked or corroded)
Dist. rotor
A malfunctioning fuel injector
A malfunctioning EGR system(causes rough idle)
A possible blown headgasket, these engines had head gasket problems and there is still a recall(limited service campaign)toyota will replace the headgaskets at no charge"If the vehicle qualifies".
The best way to find out is to call the dealer and have them run the VIN# on Toyota's tech info system, or if you don't wish to deal with them at this time email it to me and I can find out but not until late monday.