Why does the Torah insert here the Parshah of Avodah after drinking wine?
Seforno: Refer to 10:1:1:2*.
Da'as Zekenim: Wine brought death and curses to the world, exile to the 10 Shevatim, leads to awesome Aveiros - it is proper that Kohanim not drink wine before coming to serve. Moshav Zekenim - this is the only verse that begins with "Yayin", for it brought lamenting to the world - "Anavemu Invei Rosh Ashkelos Meroros Lamo."(Devarim 32:32). Nadav and Avihu had drnk wine, and the Pri Etz ha'Da'as was a grape.
What is the meaning of "Yayin v'Shechar Al Teisht"?
Rashi: It means that a Kohen may not drink wine in a manner that intoxicates 1 before performing the Avodah.
Ramban (citing Rambam), Moshav Zekenim: It means wine and beer (incorporating all intoxicating drinks).
Ramban, Moshav Zekenim citing Toras Kohanim: This excludes if it was diluted, or hepaused (did not drink a Revi'is at once). A Gezeirah Shavah "Shechar-Shechar" from Nazir excludes other intoxicants.
The Pasuk only prohibits drinking wine before entering the Heichal. What if he drinks wine before approaching the Mizbe'ach in the Azarah?
Rashi and Ramban (citing the Toras Kohanim): We learn it from washing one's hands and feet, 1 for which the Torah equates approaching the Mizbe'ach to entering the Heichal; the same applies here.
Through a Gezeirah Shavah 'Bi'as Ohel Mo'ed' from 'Bi'as Ohel Mo'ed' (Rashi).
What exactly does the Isur of entering the Ohel Mo'ed or approaching the Mizbe'ach entail?
Though according to the Rambam, it is only the Chiyuv Misah that requires performing the Avodah; the La'av applies even the moment the Kohen approaches the Mizbe'ach or enters the Heichal (Ramban).
QUESTIONS ON RASHI
Rashi writes that only wine is forbidden. What is the difference between wine and other intoxicants? (Moshav Zekenim)