Chrysler Repair: 90 Grand Voyager LE-tranny question, champion plugs, grand voyager

Question
I have a 1990 Grand Voyager SE 3.3L 6 cyl, automatic transmission. When it is cold start, the van hesitates, sounds like it is going to conk out, it has little backfire noises...about 3 times...then runs normal for 1 minute. Once I hit the 1 minute mark, it doesn't switch into gear...press on the gas and it races and goes no where for a second or two, then goes into gear and runs perfect until the next cold start. This van was sitting for 5 years without being run or started due to the death of the owner, and did have its transmission replaced a month prior to his passing. I have replaced the catalytic converter and it now has passed emissions. So my question is, what do you think this is? I want to do an oil change and a tune up. I just need to know what next as I want to be sure it is safe to drive a 2+ hour drive. Thanks for any help/info.
Tina  

Answer
A tune-up (plugs, wires, pcv valve) and a new oxygen sensor would be a good start.  Only use Champion plugs.  This is a starting point depending on wear.  With a car that sat so long and no additional information I would say start with maintenance and go from there.
Doug