If your pump is like mine, and I doubt that it is too far off, the relief valve is located on the right side behind the pulley. On mine there is a large nut, about 1 1/4 in. behind the pulley. When you take the nut off there is a spool (slide valve) and a spring. As I remember the spring comes out first and then the spool. Be sure to note which way the spool goes in. I kept putting my spool in backwards, which is why it would not come up to pressure.

There is not much to these pumps and as long as you put them back together as clean as possible and with spool in the right position I don't see any reason why it won't work. Get a 1,000 or 1,500k psi gauge and connect it to the discharge hose and see what you get for pressure. As I remember I had to make a fitting to go from the hose to the gauge. I'll check if I still have it around.