At the end of Yitro's visit with Moshe, we are told וילך לו אל ארצו, that Yitro returned to his land (Midyan). However, at the end of במדבר פרק י we find Chovav (generally assumed to be Yitro because he is also called חותן משה) discussing with Moshe whether or not he would like to join Bnei Yisrael as they enter Eretz Yisrael. How much time elapsed between Yitro's two visits with Bnei Yisrael in the desert? Why did he come back to them after his first visit? Alternatively, if one accepts the opinion of many מפרשים that Yitro's visit in this week's פרשה took place after מתן תורה, is it possible that the visit recorded here and the visit recorded in במדבר are one and the same?
יט:כב speaks of כהנים who had some role in מעמד הר סיני. Who were these כהנים, considering that the descendant of Levi and Aharon had not yet been singled out for service of Hashem?
פרק יט contains instructions to prepare Bnei Yisrael for מעמד הר סיני. Hashem gives the instructions to Moshe, and he relays them to Bnei Yisrael. In what ways do Moshe's instructions to Bnei Yisrael differ from what Hashem told him?