If your problem is it sudenly cutting off during rainy days then it is probably the wiper controll circuit board. Alot of older gm's have this problem the new board is about $30 and can be bought anywhere that sells auto parts.
http://cgi.ebay.com/ebaymotors/CHEVR...88674910QQrdZ1
Im at work and Im bored so I went ahead and found the circuit board for you. This should fix your problem I had the same problem on my 89 s10 blazer bought the new curcuit board and i have never had the problem again even in one of nourth carolinas clasic afternoon monsoons.
there are three screws, take them out then pull the cover off and the board with come out, you may need to pry where the harness meets it to get that out