I'm looking for a tutorial or whitepaper on how to Migrate DNN 3.x to 4.x (the install version only). I've searched the forums and the DNN site without any luck. Any help is appreciated.

So I did the upgrade it was actually really easy. The documentation for the entire process is found on the downloads page here:
http://www.dotnetnuke.com/LinkClick.aspx?link=http%3a%2f%2fprdownloads.sourceforge.net%2fdnn%2fDotNetNuke_4.0.3_Docs.zip%3fdownload&tabid=125&mid=2799
The document you want to look for in the zip file is named DotNetNuke Installation Guide.pdf.

Basically if you are just wanting to upgrade the "Install Version", you just need to unzip DNN4 over the top of DNN3, change a few web.config settings, change your IIS config from .NET 1.1 to .NET 2 and then launch the default.aspx page and it will initialize the upgrade. There are a few more semantics and details outlined in the documentation, so read it before you do anything.

Apparently 1and1 has upgraded their.net hosting to .net 2.0 and didn't tell anyone. Consequently, a few sites I've helped friends set up using DNN 3.2.2 are exhibiting strange behaviours:

1) sometimes they get an upgrade error saying that the assembly version doesnt match the database version (paraphrased) this is when they browse to the default.aspx file.

2) sometimes it's an error in /portal application. Sometimes this happens at the default.aspx page, sometimes it's when you click on Login. Sometimes it happens when you click an edit pencil for one of the modules, and once it even happened when I clicked logoff.

While logged in as host, I went to HOst Settings and verified that it said it was using .Net Framework 2.0.50727.42

two sites are "live" and have a lot of content, the other one is a personal site that just had a resume page on it, so I've been using that one as the guinea pig. I figured the easiest thing to do was to upgrade the 3.2.2 to the latest 4.0.3 release since there were docs around for it. I couldn't find any docs on how to make 3.2.2 work with .Net framework 2.0 If that's easier, please let me know where I can find some docs on how to do that.

I watched the "how to upgrade to 3.2" video on DNNcreative which was very helpful. I've also browsed and searched through the forums here for info as well as re-read the PDF in the docs on how to upgrade. While there is good info in there, it still fell a little short for someone like me who hasn't even downloaded the source version and is strictly concerned with the install versions.

Here are the steps I performed:
backed up database and ftp'd files from remote to local for a backup
copied the web.config (3.2.2) to a temp folder and copied the release.config (4.0.3) to the same folder and opened both in my text editor

copied the connection string from the web.config to the release config in two places: under Connection Strings for SQL 2000/2005 and also a few lines down under appSettings for SQL 2000/2005 for backwards compatibility. After that I copied & pasted the installation date key from the old config to the new one.

Next I copied the validationKey and decryptionKey values from the web.config over to the system.web area in release.config (4.0.3)

Following that, according to 1and1's FAQ (which admittedly is for v3.0.13 but the same changes applied to 3.2.2) I uncommented <identity impersonate="true"> and commented out the rest of the authentication section and then commented out the next line, which was about the maximum file size.

Finally, I changed the database owner from dbo over to my dbo123456789 username from 1and1 and saved it.

I uploaded the v4.0.3 install files and overwrote where neccessary. I did this twice, just in case, based on comments here in the forums.

After that I hit www.mysite.com/portal/default.aspx and got a runtime error. I tried www.mysite.com/portal/install/install,aspx?mode=install and got the same.

It's failing pretty fast after I click go or hit enter... Should I remove/comment out the SQL 2005 Express connection strings? can anyone think of anything else to try? Please don't say "switch hosts" because it's not an option for me :)

Once I get it working, I'm going to take my notes and some screenshots and make a step-by-step and post it up here as well as send it to 1and1 and maybe they'll include it in their FAQ section to update/supplement their setup guide which is for 3.0.13.