The uniqueness of shevet Levi is evident in the way they were counted. Initially the entire shevet was counted - "kol zechar miben chodesh vomahlah tifkedaim - every male from one month of age and up shall you count them" (Bamidbar 3:15). The bnei Levi were counted according to their age. The family of Gershon, the oldest son, was counted first, followed by the families of Kehas and Merari.
Subsequently, shevet Levi was counted again. This time Hashem commanded Moshe Rabbeinu "miben shloshim shana vomahlah v'ad ben chamishim shana, kol ba latzava la'asos melacha b'ohel moed - from thirty years of age and up, until fifty years of age, everyone who comes to join the legion to perform work in the Tent of Meeting" (Bamidbar 4:3). Because beni Levi were counted for the purpose of avodah, ONLY those who were eligible to serve in the mikdash were counted.
This time, however, the sons of Kehas, the second son of Levi, were counted first. The Medrash Rabbah comments, "lama hikdim hakasuv l'Kehas, l'fi sheKehas haya matoanei ha'aron - because the beni Kehas were granted the privilege of carrying the Aron they were counted first. The Kli Yakar (Bamidbar 4:22) explains that in order to demonstrate that "keser Torah hefker lakol, v'hakol zochin eilav" - that Torah is accessible to everyone, irrespective of one's birthright, the sons of Kehas (who was NOT the oldest son) were granted this right.
Similarly, the Rambam (Hilchos Shemittah V'yoveil 13:3) emphasizes:
V'lo shevet Levi bilvad ela kol ish v'ish. Harei zeh niskadesh kodesh kodoshim v'y'hiyeh Hashe, chelko v'nachalaso l'olam u'l'olmei olamim - Any member of Klal Yisroel who emulates the Leviim "becomes sanctified as holy of holies and Hashem will be his portion and heritage forever
Indeed the passuk in Mishlei (3:15) describes Torah as "yakara hi mipeninim - more precious than pearls." The Kli Yakar explains that the word peninim has several meanings. Peninim connotes lifnai ulivnim, a reference to the Kohein Gadol who enters the Kodesh Hakodoshim. Furthermore, peninim alludes to the keser malchus, the royal crown which contains pearls and precious stones. Additionally, peninim refers to the rights of the first born, as implied by the verse "vezos lifnim b'Yisroel" (Ruth 4:7). These allusions underscore the primacy and accessibility of Torah.
The Ramban (Shemos 25:10) notes that the commandment to construct the Aron is written in the plural - "v'assu Aron - and they shall make an Aron." Everyone was called upon to participate in creating the Aron. The Medrash explains "yavo'u hakol v'yisasku baron shyizku laTorah - everyone should come and be involved in the Aron so they should merit acquiring Torah". May we be worthy of this unique privilege.