how do i get codes on 86 yoda 22r truck?

truck is running rich and will not idle, just got the truck so dont know much about yodas, previous owner says its the egr valve, cannot afford $200.00 for valve, i payed $200.00 for the truck, just need to know how to get codes and how to dicifer them and maybe fix it cheaper than i payed for the truck
thanks guys for any help