Help with DNS settings

My dad recently bought a mac mini server for his office and entrusted me to set it up for him. I bought the snow leopard server for dummies book and have read up on everything but one area that is still confusing is DNS. When doing the initial configuration and setup, I come to the Network Names screen. Now the book gives three different options for this screen:

A. If you have a DNS server on your network, the info will already be filled in.

B. If you don't have a DNS server, and you don't get DNS service from an ISP, your mac will be the DNS server. Register a domain name and enter a fully qualified DNS name similar to this: myserver.acme.com.

C. If you don't have a DNS server, and only the local network access the server, then you can make up a name.

So I have a few questions.

1. We want to be able to access the files on the server from home, so I'm assuming we should
choose option B so the server will be available on the internet. However, I also assume that we currently get DNS service from our ISP, so if we choose option B, will the mac mini server become our DNS server instead of the ISP's DNS servers?

2. We have a website at alpinemaintenance.com. I assume this will work for the registered domain name needed in option 2. So do I enter something similar to myserver.alpinemaintenance.com?

3. My dad does not want to use this server to host our website or email services right now. By using that registered domain name for this server, will it automatically make our mac mini server the web and email server? I'm assuming not since records would have to be changed.

I'm pretty experienced with macs in general but new to Mac OS X Server, and I'll probably have more questions once these get answered.
Thanks for your patience.