I just purchased a windows server 2008 R2 dedicated server from a local vendor. The server will also include SQL Server Web Edition Licence.
I have so little experience on servers and a little above basic info on IIS. I will be ruining asp.net applications on our server and there will be about 13 applications running on the server.
So where should I start here? should I firstly install IIS from control panel? or should I firstly install DNS server?
I would definitely outsource DNS. Get a vendor like dyndns.com and have them point to your IP addresses(s). If you're going to handle this yourself then keep to just the IIS website/application part of it.
I've been working on a 52 week series for the web pro. I walk through host headers, IIS in depth, DNS and various other tools and tricks for the web pro. You may find this useful to answer a number of your 'getting started' (and then more advanced) questions.
http://weblogs.asp.net/owscott/archive/tags/Web+Pro+Series/default.aspx