need help fixing leaking windows on areostar van

[lightspeed]

hi on my ford areostar van , which i am going to fix into a mini campervan . In hard and medium "rain " my side sliding window (drivers side middle of van )and two side rear windows (back of the van ) and even the rear back window glass seems to leak . Me and my wife stayed in our van for about 5 days to see my mother in a nursing home . when it rained it started dripping inside from the window area and or the plastic molding around the window inside .
I have been looking on many forums on the internet about what to do as a fix for this the van is a 1992 .
i have recently bought some thick plywood and two by fours to make a bed and frame which will come from the rear back door up to the back of the sliding side door .
don't know why i can't find anything but i have looked high and low on a fix for this does anyone have any idea what needs to be fixed and how it can be done ? or a website ? any help on this would be appreciated ... "Alot !!"
later after the bed is fixed from their since i knw for sure how much room will be left i plan on buying or making a cabinet to put a sink in and a place for a door to put my portable toilet under when not in use . i plan on using wood screws to put things together that way i can take it apart ( the bed ) to use in a larger van if i ever get one .

[markopolo]

I've read of RV'ers having good results using Capt. Tolley's Creeping Crack Cure http://www.captaintolley.com/ sealing leaks around fixed windows. I don't know about the sliding window though.