Concerns about my new '88 Galant

I just got an 88 Galant Sigma... and I love it to death. However, I'm concerned about the engine. I noticed it slightly on the test drive, but am noticing it Alot more after the 50 mile trek home. It seems to hesitate/vibrate as I accelerate. It will also do it in park between 2500 and 3500 RPM... Another thing I noticed, although I will be doing an oil change on it tomorrow, when I pulled out the dipstick, smoke was coming out of the hole where the dipstick was. Is this normal? I had only driven the car about 3 miles and the temperature was still in the lower portion of the normal setting. The car as about 90k miles on it, but the previous owner does not know if the timing belt was changed on it. Anyone know when the recommended servicing is for that belt and approximately what it costs to have it replaced? Thanks in advance for all the help!

Timing belts should generally be changed about every 60,000 miles. Some newer cars have intervals of 80,000, but I've never heard f anything higher. I reckon if you've got 90k out of it, it's had a good run and a new one won't do it any harm.

PS; My Galant has done nearly 115,000 and is on it's SECOND new cambelt ! If you have a 4G63 DOHC, you'll also need to change the balance shaft belt at the same time. Not sure what they cost in the US, but I got both of mine [cambelt & balance shaft belt] for less than GB£40.