I'm planning to migrate next weekend. I've calculated it will take 7-8 hours to import the data. Should I completely close the board or could I just disable registration, pm, posting etc? Thus preserving traffic, won't confuse google and members/visitors can still read.
Can I install xenforo in a folder off the root directory of the old forum, get it configured, import the data, then delete the old forum files at the root and reupload the xenforo files to the root and it should work?
You actually don't need to re-upload anything. All you need to do it move the install directory and then update it in ACP.
For reference, this is how I do a test site based off the live site:
1) Make copy of database & assign DB username/password
2) zip entire XF install directory
3) create new password protected directory
4) unzip XF install into that directory
5) edit config file to reflect copied database
6) go to url, enter ACP, change board path
So for a fresh install it's actually just move the contents, then step 6.