Would like some information on the installation of this mod. Is it an installable package?
Yes
Are there any manual changes needed for custom themes?
Yes
Any clashes with other mods?
It already clashes with SMF itself, on certain versions.......

Also, what are the advantages a user gets by connecting an existing SMF account to their facebook profile?
None. It just has a Facebook icon in the user details next to messages. It links to your FB account profile.
I mentioned a list of possible additions to Dragooon, but apparently he's not interested.
http://smf-media.com/community/index.php?topic=1224.msg9479#msg9479I myself have been interested in doing a free FB mod for some time but Dragooon did it before me. What I was interested in was not in doing a mod for logging in, but a mod for retrieving user status and other things like that. I'm guessing I should make a completely different mod or something, since I won't make a free mod that requires a pay-for mod as a basis (see what I mean?)...
Sorry Dragooon, but without any more features, I don't think that mod is worth $20. Maybe $10, but really at most. You should consider adding (many) more features. I'm ready to help if you set up a private SVN for your source code as well.
How does the "sync buddies" feature work?
I guess it will check other users on the board who have linked to their FB account. If one of them is in your buddy list on FB, it will add them to your buddy list on SMF. Meaning you'll have to resync from time to time to get new friends or something.
What information from SMF can be posted on facebook once the accounts are linked?
None.