I'll do my best to answer all these as completely as possible. Some of my answers might not be the answers he's looking for, but hopefully they'll make sense.
Before I start, however, I'll state a few things about how this system works:
1) We manage the database, php code, and hosting. You, as a user will not have access to either the database, or the php code that runs behind the scenes.
1. what happens to the current database?
It all depends. I'm not familiar with the structure of phpnuke, but it's safe to say that it's incompatible. As such, your database will stay at your current host, and a completely new one will be created for you here.
2. what happens to the current gallery2?
Undoubtedly, you'll have to upload each gallery picture again.
3. what happens to the current site's template?
It depends on how comfortable you (or your guild members, or whoever) are with HTML and CSS. The template system for phpnuke is not compatible with our specifically-build templating system. That said, however, someone with some HTML experience can fairly easily convert one website's template to fit ours with a few hours work. It's certainly WAY easier than trying to do it from scratch and making the graphics.
Our templating system is different because it's specific to our system. It utilizes all the tools of the site and has all the addons integrated into it, just as everything on this site has everything integrated.
4. who maintains the site?
If by "Maintains," you mean deals with the php code and does hardware upgrades and software upgrades, then that would be me.
5. who manages the site?
If by "Manages" you mean deals with things like Roster, deleting posts, managing DKP, etc, than that would be you, and whoever you give access to (our "Feature Access" section is a security section that allows you to designate which ranks have access to which Administrative features).
6. who has full access to the database?
Me and only me.
7. if you all don't maintain the site then why is there a monthly $10 dollar fee?
That's answered already, however it's worth noting that there isn't EXACTLY A monthly fee. It's a yearly fee paid in advance, but there's a no-hassle cancellation policy: cancelling is as easy and clicking the "Cancel Service" button on your Admin menu.
8. what happens to the current flash chat that he is using?
If he's in love with the flash chat, he can probably stick into a custom page, otherwise, we have a built-in chat feature.
9. are there much add-ons to add on for each feature?
Everything available to you on the site is a few clicks away. Want to add a "Shoutbox"? Head to the Menu Administration section and check a box and give it a title. Want to put your Guild Bank on the website, simplt designate a character (or characters) as guild bank and that information will be displayed in a special guild bank section.
The simple way to describe it is this:
The Base system ($20/yr) includes every feature on the site except for two: The Forums and the DKP/Loot Systems. There are no additional fees or costs (unless you want to pay someone to do custom design work for you, but we don't offer that as a service).
The Forum costs and additional $30/year, and the DKP system costs and additional $30/yr. Finally, if you want to allow your users to be able to upload files to the forum (pictures, small videos, etc) to your forum, then that's an additional $30/yr and is primarily for paying for the added space and bandwidth utilization.
10. is this just like php?
Our "Advanced Layout Options" act as a sort of scripting language more in line with a markup language like HTML. Users have no php-level access.
11. are skins/themes free or does he have to pay for them on top of the $10/month?
At the moment, the best that can be done without diving into HTML code (using the Advanced Layout Options) is the ability to quickly choose a color scheme, logo, background image, and other such simple functions. Advanced Drop-In Templates are in the work, but are pretty much top priority right now, and should be ready very soon.
12. does he have to change servers?
Yes, but it's going to be fairly transparent. As we manage everything, it works like this: You sign up, you pay, then you log in to your site and do what you need to do. There's no FTPing in and configuring database and server configurations. It's all configured. You just say who has access to which features, customize your look, upload your roster, and you're good to go.
Are there in depth information on how to convert as well as better documentation than what is on this site? I don't see much of "easily switch from phpnuke sites to dkpsystems" or "your fee's applies to these area's".
I'm afraid there's no walkthrough for switching from phpnuke to this. The best we have, in that regard, is if you use eqDKP for DKP tracking, we have an eqDKP importer for you, and if you have a phpBB forum, then you can import that database into your forum as well.
Hopefully my explanations make sense.
If you have any further questions, don't hesitate to ask.