Why did Moshe discuss the Mitzvah of Shemiras Shabbos before the Meleches ha'Mishkan?
Rashi, Ramban and Seforno: To teach us that building the Mishkan does not override Shabbos. 1
Because the sanctity of time is greater than that of location. See also Ba'al ha'Turim.
Why does the Torah write "Te'aseh Melachah" and not Ta'ase Melachah"?
Oznayim la'Torah: Because it is not an individual Mitzvah to work during the week but a collective one to ensure that work is done during the week exclusively, but not on Shabbos. 1
Having already taught us (in Ki Sisa, Sh'mos, 31:14) that Chilul Shabbos is subject to the death-penalty, why does the Torah see fit to repeat it here?
Seforno: To teach us that one is Chayav Misah even though he was performing a Mitzvah.
Mechilta: Because we would otherwise have thought that when Hashem said "Ve'asu Li Mikdash", He meant even on Shabbos. 1
Torah Temimah: Seeing as, once it has been built, bringing the Korbanos does override Shabbos. Or because now that we have access to Kedushas ha'Makom during the entire week, Kedushas ha'Zeman only once a week is no longer necessary (Oznayim la'Torah). This is not correct however, since Shabbos applies even where there is no Beis-Hamikdash and even when it is not standing (Oznayim la'Torah).
Why are the implications of the word "Yih'yeh lachem Kodesh"?
Mechilta: 'It is holy for you (for your private affairs) but mundane for (matters that concern) Hashem
Why does it say "Te'aseh Melachah" (passive)?
Moshav Zekenim: When Yisrael merits, our work is done through others.
Why does it say here Kodesh before Shabbos Shabason, and above (16:23) it says "Shabason Shabbos Kodesh"?
Moshav Zekenim (16:23): This teaches that one must add from Chol onto Kodesh. Shevisah (refraining from Melachah) before the actual Kodesh, and also after the Kodesh (on Motza'ei Shabbos).
QUESTIONS ON RASHI
Rashi writes that here the Torah teaches that building the Mishkan does not override Shabbos. Why is this needed? Shabbos is an Aseh and Lo Sa'aseh. An Aseh does not override an Aseh and Lo Sa'aseh (Bava Metzi'a 30a).
Tosfos (Yevamos 6a DH Nigamer): (Normally an Aseh does not override an Aseh and Lo Sa'aseh, for one Aseh no stronger than another.) Building the Mikdash is stronger than the Aseh of Shabbos, due to fear of the Mikdash.
Ritva (Yevamos 6a, citing R. Yonah): The Aseh of Shabbos applies only to Av Melachos that are stringent. 1
Torah Temimah: Refer to 35:2:2:2*.
One might have thought that Binyan ha'Mishkan overrides Toldos, or making animals work
Rashi writes that here the Torah teaches that building the Mishkan does not override Shabbos. We already know this from (Vayikra 19:30) "Es Shabsosai Tishmoru u'Makdishi Tira'u" (Yevamos 6a)!
Moshav Zekenim: Our verse teaches that all the Melachos used to make the Mishkan are forbidden on Shabbos.