1)
How will they serve in the Mikdash?
1.
Radak: They will oversee the gates and do Shechitah, which Zarim may do. However, they will not offer Korbanos.
2.
Malbim: They will serve the gatekeepers, but they themselves will not be gatekeepers.
2)
Will Leviyim slaughter the Olah?
1.
Rashi: Yes. Even Zarim, slaves and women may do Shechitah.
2.
Radak: No. This refers to Kohanim [who served idolatry. They will do only service such as Shechitah, which a Zar may do.
3)
To whom does "Lifneihem" refer?
1.
Malbim: In front of the nation, to serve them in needs of bringing the Korban, e.g. Shechitah, flaying and dissecting, and other matters [that may be] done via Zarim.
