1992 Plymouth Voyager Sometimes it will work and others it

My tranny will sometimes either not work at all, not shift properly in and out of second gear or it will slip gears.I am trying to figure out it it just needs a good transmission flush or if it needs rebuilt. Someone told me that it could possibly be the transmission control module. Any sugestions?Please help I use this for my childrens dr visits. Is the van worth saving or should I find a new vehicle?