  In this paper the building blocks for the two-loop renormalization of the
Standard Model are introduced with a comprehensive discussion of the special
vertices induced in the Lagrangian by a particular diagonalization of the
neutral sector and by two alternative treatments of the Higgs tadpoles. Dyson
resummed propagators for the gauge bosons are derived, and two-loop
Ward-Slavnov-Taylor identities are discussed. In part II, the complete set of
counterterms needed for the two-loop renormalization will be derived. In part
III, a renormalization scheme will be introduced, connecting the renormalized
quantities to an input parameter set of (pseudo-)experimental data, critically
discussing renormalization of a gauge theory with unstable particles.
