I happen to be a gabbai in my shul, and over Pesach two interesting shailos came up.
1) On Shabbos Chol HaMoed, the chazzan was given the maftir sefer torah. The question is, can you switch the sifrei torah or must you read the regular leining from teh maftir torah (and vice versa) . This would obviously necessitate rolling the maftir torah to the regular leining and rolling the regular torah to maftir.
The Piskei Teshuvos (which happens to be a great reference sefer for times like these) quotes a Biur Halacha in Hilchos Chanuka and a Prim Migadim in Hilchos Kriyas HaTorah that one can switch teh torahs. Not only that the Biur Halacha says even if you already opened the wrong sefer up you can roll it back up and exchange it for the right sefer.
2) On Chol Hamoed Pesach you don't recite kaddish until after you read the second sefer. Should you put the first sefer back on the shulchan before saying Kaddish?
Once again the Piskei Teshuvos provides the answer. It is a machlokes Magan Avraham and Pri Megadim. The MG"A says on a day when you read 3 sifrei torah and kaddish is said after the second sefer, you should put all 3 on the bima. The Pri Megadim says you only need to put the last two on the bima. It would come out in our case the MG"A would say to put both on the bima and teh Pri Megadim needs only the second one on the bima. It seems the minhag haolam is like the Pri Megadim.