My question is the following,would the scalar of precession of Mercury orbit be the same if Mercury orbited Sun in the oposit direction?
General relativity is only one cause of the precession of Mercury's orbit, and not the largest factor. Gravitational perturbation by the other planets and the non-spherical sun also cause precession. Newtonian gravity predicts precession of 532 arcseconds per century, but 575 arcseconds is observed. The discrepancy can be explained if one uses General Relativity as the model of gravity.
The extra precession of 43 arcseconds caused by GR would be the same, the perturbations due to the other planets would not be the same, unless they were also orbiting the sun in the opposite direction.