Your truck is a worthy off-road vehicle in stock form. Depending on how much you want to invest in that old a vehicle is up to you. Also, what is the general overall conditon of the truck and how well has it been maintained is an important factor. If your just getting into off-roading go slowly. I would change all the fluids, belts, hoses etc and a good tune up. Then invest in a good set of tires, shocks and if the rims are stock, go to a larger size for the bigger tires. Due to you engine size, no larger than 31-10/50 x15.
There numerous posts on this site w/good advice based on practical experience-check them out.