Red Bud is an awesome time - I hope you can make it! I've been there for the National 6 years and counting and Red's been there around 8-9 years and counting. I'll try to answer your questions...
Brainerd, MN... does your friend ride/race? There is a SWEET track 30 miles west from there in Staples, MN, that I've raced a couple of times. I would love to get back up there one day again! I think 8.5-9.5 hours sounds about right. 2.5 hours to Minneapolis, 4 hours to Madison, 4-5 hours to Red Bud. Just make sure you don't come across from Madison to Red Bud during Chicago rush hour as it can get very ugly... especially the 40 mile stretch across I-80 in Indiana. If you can drive that in the middle of the night... do it!
If you get there by Saturday AM, that should be enough time for the full effect. The only thing that happens Friday is amateur races on the night track but there is no access to the Pro track. The Pros go out for practice on Saturday early afternoon and this is an awesome time to get roosted by guys like RC and Bubba or get some excellent pictures. If you go in the pits, they are pretty empty on Saturday as well. Then Saturday there are also amateur races on the night track. Saturday night used to be a party like you couldn't even imagine but they have really stepped it down over the past 3 years so now it's really tame.
In the past, the fireworks have always been Saturday night only. This year, if I remember right, they had them both Friday and Saturday because Friday was actually the 4th of July. So I'm guessing next year the big fireworks display will only be Saturday night.
The closest airports are South Bend (15 mi.), Midway (100 mi.), Grand Rapids (110 mi.), O'hare (115 mi.), Indy (160 mi.), Detroit (190 mi.). You'll probably have a hard time finding a flight into South Bend or Grand Rapids as they are very small airports, so the two Chicago airports are your best bet (Midway and O'hare).
Hopefully my answers will help ya get started... if you have more questions, just ask!
Also, check out
www.redbudmx.com for details on the 2003 Nationals weekend.