Hello,
I just posted the following to another question and figured it may help you as well so I am coppying it here too.
The gourds can be put it the garage, or just left outside on the vine all winter. They actually dry faster when left on the vine all winter. You can green clean too. The only thin you have to be worried about doing that is if you want seed for next year. If the seeds freeze they may not germinate. All you need to do there is take the gourd you want for seed into the garage and they should be just fine. Do be careful with the mold. My post below explains the mold and I'll put in a link to our web site too.

We clean our gourds with a chore boy scubber. Don't be afraid to scub that gourd hard. You won't hurt the gourd. From looking at the pic, the top apears to have the tuff waxy skin on it, you may want to soak it for a bit. I can tell once you get all the skin off of it, it's going to be awesome! The shell is a nice colour under that skin. You can see it in patches. The shell of a gourd is just like wood in most cases. To clean the inside.. That can be easy, or it can be very hard, depending on the insides of the particular gourd. I have had some gourds that are nothing more than a thin layer that had nicely peeled itself away from the inside of the gourd. I have also had gourds that the inside a thick wall of white foamy stuff clued tight to the inside. My favorites are the ones that the insides just ball up around all the seeds. You get a seed ball that you just dumb in thrash. Then do some sanding to make it smooth. For the hard to get out insides, we use a wire, or sand paper brush thing with our drill. That takes it all out pretty fast.
I too forgot about the paper bags. I like to use cut up pieces of fabric and decopouge them on the inside.
My DH wrote a couple of booklets on gourds if anyone is interested you can download them in PDF format, we also have a gourd chart that can be downloaded. Just click the link below. All three are free.
Also, gourds are wonderful canvas's given to us from God, but you have to be careful when working with them. Gourds as they dry grow mold on the surface skin. It may be white mold, green mold, black mold, or any other number of colors. You must always wear a resporator. Not one of those paper face mask either, you need one of those good gas mask looking resporators. The inside of the gourd can have some real nasty mold in it as well. There usualy is no mold inside, but it does happen. Regardless if there is mold or not, you still need the resporator as the stuff inside the gourd, as well as the dust from cutting and sanding on a gourd can make you deathly ill. I am not trying to scare anyone, but it is important to know the safety issues of gourds and exercise proper precautions. My husband and I have been crafting gourds for close to 15 years now, and believe me we found all this out the hard way! Hubby still has breathing problems from the gourd dust he breathed in a few years ago when he decided that he could sand a little spot on a gourd "Real fast" without his resporator! A good way to know if your resporator is a good one is if you can smell and taste the gourd dust as you breath in and out, then your resporator is not filtering everything out. Check out our gourd site, it has lots of really good info on it about gourds, mold, drying, cleaning, and crafting. Links to the gourd booklet, (Gourd reports) are on the left side of the page, along with links to the mold info, gourd charts and gourd report 2

Here is a link that might be useful: The Gourd Reserve

I also live in s. MN. and I dry them in all 3 of our sheds and have also found some outside in the garden in the spring. I guess I missed a few. They are all ok. If they don't make it it wasn't caused by the our winters but that they weren't mature. If I want to save certain seeds I green clean them and dry indoors away from everyone.
Good luck with them and make sure the stem is totally dry before picking.
Sue in MN

I'm in zone 4 and have never had luck leaving the gourds outdoor all winter. They were ripe, the vines had shriveled, but they still froze. When they defrosted in the spring they rotted. Now I never take a chance. I bring them in and dry them in the barn.