How much for a 1.03 ct round center stone ring G Color I1 clarity 3 full carats total?

Your trove is worth whatever someone will pay you for it.

You can purchase a center stone today at Blue Nile, and pay between $US3,980 and US$8,013, for a diamond of this colour and carat weight, but with higher clarity grade -- SI1 -- depending on the quality of the cut.

(I1 clarity is a lower-than-desirable clarity, given that the inclusion is clearly visible.)

The remaining gemstones are best evaluated by a gemologist, as are the best practices for you evaluating the center stone.