The 3.5 liter engine is an interference fit engine which means it will do serious dmage if the timing belt fails, that being said the belt should last 105,000 miles under normal driving conditions. I wonder why the belt failed in such a short time?
Is the rest of the van in good order, transmission shift OK, tires good ect....?
A friend of mine says the devil you know is better than the devil you don't. You have had this car a while and know it was otherwise reliable, you could buy another minivan for $4000 and be buying someone elses problems.
These engines can be successfully rebuilt and run as good as new. Ask the shop repairing the van to look it over first to see if the axles are OK, steering rack leaks, brakes and tires are OK ect.. ask them just to look it over and see if they foresee any other problems you may run into with the van in the near future.