REAR SUSPENSION TOWN & COUNTRY MINI VAN

The suspension has been raised 1 & 1/2 inches by using after market springs. This causes the van to ride so rough even under 10 MPH that you just want to park it. This Van is converted for Handicap use for my wife. I want to improve the ride as much as possible.
Can I go back to the OEM springs and use a spacer to lift it but have a better ride?
Does raising cause the shocks not to work properly?
Do I need to also raise the front?
I have been trying to learn as much as possible, but can not get the help from the companies that should be able to tell me what to do.
Any help you can give will be much appreciated.
Paul Jennings