Hi Robert,
That's a great combo for the owls, especially the 600.
I live in Minnesota and have gone there for about 10 years a few times each winter and in summer too.
A couple of things:
Check out the information online at Friends of Sax Zim bog; they have a FB page, and a helpful page for planning the visit too:
https://saxzim.org.
Your best bet is early and evening; owls are often seen along County Road 7, and McDavitt and Admiral Roads, just scan the tree tops. You can also stop in at the Welcome Center along Owl Ave. starting December 1st.
It is wonderful for other birds too at feeders; evening grosbeaks are relaible each morning until about 10 am at Mary Lou's feeders, a private resideance (her neighbors across the street are mean so just ignore them).
The welcome center will clue you in on what is being seen, but the best help is to get the "Messgner" app - you can download it, and load it in your iphone; on it people report in real time what they are seeing, so leave it open as you drive about the bog.
For lodging I like to stay in Cloquet; it's about a half hour from the bog, and has a few good places to stay at.
Great grays are residents, but as we get into winter sometimes more birds show up for the winter. I have not heard of snowies yet. Hawk owls usually show up too in the bog and are a diurnal bird so you can see them more during the day.
Really it's just about patience and driving slowly and frankly looking for the pulled over vehicle too or photographer looking up at the tree(s)
I hope to get up there in early January and then a time or two after that.
Kim Risen is also a wonderful guide who I've worked with if you'd like to have someone to be a second set of eyes and he knows the area well.
Best of luck!
Paul