1) The Chasam Sofer quotes from R' Ya'akov Emden that Moshe Rabeinu was born on 7 Adar on Shabbos, making his yom hamilah on Shabbos 14 Adar. Since Moshe was born mahul, all that was required was hatafas dam bris, which was done on 15 Adar (the hatafah in this case is not doche Shabbos). Therefore, these two days of 14/15 Adar are days of simcha for all future generations.
The C"S is not completely happy with this idea -- why should 14 Adar should be a special day if no milah was done? You can't celebrate a non-event! He therefore suggests a different reason why that day is special. In Parshas Nitzavim, the last day of Moshe Rabeinu's life, Moshe gave a sefer Torah to sheveit Levi. The other shevatim complained -- why was Levi alone worthy of such a gift? It was about that day that Moshe said, "Lo nasam Hashem lachem lev lada'as ad hayom ha'zeh," which Rashi explains to mean that the people finally arrived at an understanding of da'as rabbam. This was a day of kabbalas haTorah, a true cause for celebration! The problem was that it is also the day of Moshe Rabeinu's petirah. Before the celebration could begin, aveilus set in. A week later, when the period of shiva ended, on 14 Adar, this kabbalas haTorah could be properly commemorated. The reverberations of that simcha were felt generations later -- "hadar kiblu'hu b'ymei Achashveirosh." (The C"S further ties this in with the parsha's opening -- take a look.)
2) The opening of the parsha is replete with difficulties and diyukim. The command to take oil to light the menorah seems out of place, sandwiched here between the construction of the mishkan and the making of bigdei kehunah. The format of parsha -- Hashem telling Moshe that he will teach a mitzvah to Bnei Yisrael -- is unique; in all other places Moshe simply relates the mitzvah or is commanded (i.e. the imperative is used, as opposed to the future tense, the way it is used here) to instruct Bnei Yisrael. The special emphasis on Moshe's personal role -- "atah titzaveh," "v'yikchu eilecha" -- is striking. Hopefully I've piqued your curiosity and you have some time to dig through the meforshim this Shabbos. Since it is not yet Shabos I haven't had time to do all my digging, so I just want one to share with you one beautiful remez of the Maor v'Shemesh.
"Titzaveh" is related to the same root as the word "tzavsah," to connect, to join -- Moshe was commanded to join with, to connect with Bnei Yisrael. It goes without saying that the closer our leaders are to us, the greater our benefit. But it's not only we who benefit. "V'yikchu eilecha" -- the people also bring something to Moshe, namely, "shemen zayis zach," pure oil, symbolizing refined knowledge and wisdom, "kasis la'maor," made from beaten olives, symbolizing humility. Just as we grow from our leaders, they in turn grow from our attention and dedication.