  We compute the complete gauge and chiral superheavy mass spectrum and
couplings of the Minimal Susy GUT (based on the $ \bf {210- \oot- 126-10}$
irreps as the Higgs system) by decomposing SO(10) labels in terms of Pati Salam
subgroup labels. The spectra are sensitive functions of the single complex
parameter that controls MSGUT symmetry breaking. We scan for the dependence of
the threshold corrections to the Weinberg angle and Unification scale as
functions of this parameter. We find that for generic values of the GUT scale
parameters the modifications are within 10% of the one loop values and can be
much smaller for significant regions of the parameter space. This shows that
contrary to longstanding conjectures, high precision calculations are not
futile but rather necessary and feasible in the MSGUT. The couplings of the
matter supermultiplets are made explicit and used to identify the channels for
exotic ($\Delta B\neq 0$) processes and to write down the associated bare $d=5$
operators (some of both are novel). The mass formulae for all matter fermions
are derived. This sets the stage for a comprehensive RG based phenomenological
analysis of the MSGUT.
