Another MN homeschooler here! If you join MHA (Minnesota Homeschoolers Alliance http://www.homeschoolers.org/
)) for $25/year, you get a great packet of information about homeschooling in general and homeschooling in Minnesota. Plus you get several other things like discounts, a quarterly magazine, mailing list of events in the area, etc. You can check it all out on their page.
Also, there are a couple of yahoo lists in the Twin Cities area. One is ECHO-MN which is a great list and HSAdventures which is generally strictly events and field trips for homeschoolers.
I don't do boxed curriculum. I pull my curriculum from a variety of resources. Do I miss stuff? Yeah, I never go long without realizing what I'm missing or could be doing better and I research available curriculum and add it to our day. I pull stuff from workbooks, the internet, online games and lessons plans, library books - literally everywhere I can find it. If there's something you think your DC should be learning, toss it in. As long as you're covering the subjects required by law, you should be fine. I find that most homeschoolers easily go well beyond the minimum legal requirements - it's not hard to do. I have a blast homeschooling my kids. We never have a shortage of things to do and we have time to do things that other kids don't.
It does sound overwhelming at first, but with a 1st grader, we cover reading, spelling, writing, language arts (grammar), science, math, social studies, science, geography, art, music, Spanish, sign language, French, and phy ed. That sounds like a ton but we do each subject in 10 min increments and we don't do every subject every day. Obviously you would be able to tweak that with a 5th grader as their attention spans are longer but I'm sure you'll find a system that works for you and don't be afraid to yell for help. We've all been there - we've all looked around and thought "what did I do?" but once you find your groove, you'll be fine.
I can't answer your question about testing, unfortunately as I have a year old. I haven't even had to fill out the paperwork yet as he has not reached compulsory age in MN - that'll happen this fall when he turns 7.
Oh, and if you decide to join MHA, take your MHA card to Barnes & Noble and get your Educator's discount card. You get 20% off school related books and 4 times a year they have Educator's Week with all kinds of sales and events.
Borders may have a similar program as well. I don't have a Borders where I live so I'm not entirely sure on that one.