1995 Ford Aerostar Transmission shudders

My van has become my in-town, flat steets only vehicle. The van does not accelerate smoothly--it shudders. In the hot Phoenix summer months it really shudders. The shuddering usually occurs around 20-35 mph. If you don't force it, the van will finally accelerate fine. So, I am usually the one everybody is going around at the light.

My mechanic of 28 years has done the lesser type maintenance on the transmission, and while he hasn't said it is time to overhaul it, he has said he can recommend someone when I am ready for this repair.

I would like your opinion on the shuddering. I would also like a ballpark figure on the cost. Last, is it worth repairing?

The maintenance has been done regularly and the repairs have been done as soon as the problem arises. There has been a pesky, reoccurring problem with the panel lights-"brake" and "Rear ABS" lights- which has been worked on numerous times. The brakes are fine, the lights keep turning on at odd times.

With the Cash for Clunkers I am really thinking about a new vehicle!