How do I find how to wire a new blower motor and other wiring for my Sears furnace?

On my furnaces there are wiring diagrams on the inside of the control panel. Poke around and you may be in luck.

I have also seen that some manufacturers have downloadable materials on their website (not sure about sears but you should look at who manufacturers the control unit/curcuit board and it is likely they will have it online - honeywell did for me)