Water leak

89 6 cyl 2.8 auto trans I have a leak some where I cant seem to find do you know if these cars are prone to leaking from the windows doors firewall it gets wet every time it rains it is not the heater core I bought it from my neighbor it set up 2yrs because he gave up on it it was full of mold and every floor board was flooded I think it is the windows probably the rear side windows anyway is there a certain way to take off the trim do I pop it off or slide it or what have no idea I dont want to break the trim it looks kinda nice now dont want to mess it up and I wanted to see if there is a known problem with this car short of drilling a hole in the floor I got to fix this before winter or im going to be chunking out ice like when I bought this thing oh and if I get that fixed do you know of something that will get that smell out /mold/ its not bad now cant smell it now untill it rains and gets wet again I keep spraying lysol in it that stinks enough I have to let it air out before I can get in it.