SharePoint licensing is almost a black art. You can get an idea of the list prices but things vary depending on how many people, who you buy it from, and how it is licensed.
Here is a good calculator, but understand what you are clicking.
With MOSS you need CALs. There is a Std CAL and then if you use MOSS Enterprise there is an add-on Enterprise CAL.
There is no one server topology. Everything depends on what you plan to do with it, how many people, etc. I generally don't like to use 2 server deployments (SP, SQL) even in non-production environments. You are better off getting two smaller servers and separating the roles in most cases.
Before I made the jump from 2003 to 2007 for my first MOSS farm I probably spent 4-5 months planning it and taking it through scenarios. I would encourage you to do some homework or bring in an outside expert. Here is a good place to start if you want to read the docs: http://technet.microsoft.com/en-us/library/cc261834.aspx