I think I would start by putting in your original help files then let the users go crazy. A Wiki is a great idea - much more useful than a forum.
This was written on the Wiki. Uhhh....no. This is just my opinion, but I have looked at the Wiki a few times, and have never really gotten much out of it. The forum, however has allowed me to learn tons about AC, life, medicine, everything.
Again, my opinion, but I don't think a Wiki works well as a user guide or a FAQ. For that you need...ummm...a user's guide or a FAQ.
If you look at Wikipedia, it has a topic. Say....the Chicago Blacksox or Blue Whales. People continue to edit and contribute and soon sort of like a bell curve, it gets better and better. That doesn't work the same for questions and answers and user guide.
There are just too many ways to do the same thing and different setups. Or it is obvious how to do it. But, just look at the question on how to network. How many times have we gotten into that? At least 50. So, someone writes this wonderful networking wiki. Then, Adam comes along and edits it by changing the peer to peer to client/server. Or one person talks about faxing from their desktop. George comes in with Snappy Fax, I talk against the Brother fax and Adam talks about Muratec.
I don't know...I just don't see it as being useful. I love the interplay on here and enjoy spending hours helping others. Someone can ask me a specific question on here or by PM or even by email which is in my profile, and I will get back to them that day. I'll even remote into their computer.
I doubt we will ever have a great Wiki. But, we will always have a great forum.
Now, don't get me wrong. A very detailed user guide would be helpful. I know a lot of companies allow you to download a Quick Guide pdf and then an Admin PDF.