It is interesting that Parshas Tzav uses the word "vayakrev" ("and he brought near [offered]") in relation to the inaugural korbonos as well as in reference to Aharon and his sons. ("Vayakrev es ail ha-olah" - "And he offered the ram of elevation" [Shmos 8:18]; "Vayakrev es ha-ayil ha-sheni" - "And he offered the second ram" [ibid. v. 22]; "Vayakrev es Bnei Aharon" - "And he offered the sons of Aharon" [ibid. v. 24]; "Vayakrev Moshe es Aharon v'es banav" - "And Moshe offered Aharon and his sons" [ibid. v. 6]. This phraseology appears repeatedly and interchangably throughout the latter four aliyos in reference to the Kohanim and the korbonos.) The specific nomenclature makes it apparent that the Kohanim were not merely employees in the Mishkan, nor were they just sanctified servants. Rather, they became uniquely elevated to Avodas HaKodesh (generically similar to korbonos), attaining a superior level of sanctity as a prerequisite for their roles. (This dovetails with the ideas elaborated upon in Parshas Tetzaveh.) Thus, similar to the korbonos depicted in the first part of the parshah, the Kohanim were made close to Hashem and thereby elevated to Avodah, and for this reason their inauguration comprises the balance of Parshas Tzav, as a direct parallel to the korbonos.
We learn from this that to be a "regular" in Hashem's house necessitates that one elevate oneself so as to be worthy of constant exposure to Hashem's holiness. Recognition of the place and activity in which one is engaged mandates that one comport to a state of mind, body and spirit in consonance with the environs and role. Furthermore, just as the Kohanim were sequestered in the Mishkan for a full week (see Targum Yonasan ben Uziel on 8:33) in preparation for entry to full-time service, all who aspire to be active in the courts of Hashem - whether it be in the beis medrash, beis knesses or Beis HaMikdash itself - must prepare themselves for such and be highly-sensitized to the kedusha of their surroundings and the nature of their tasks. Lack of proper decorum in mekomos kedoshim (holy places) is not merely disrespectful; it is defiant of the entire purpose of being in such venues and it negates the quality of one's activity there, for just as the Kohanim required extensive preparation and sanctification for the very Avodah to be meaningful, lack of personal preparation and seriousness in the places of our avodah constitutes a lack in the very avodah itself.