Adventure mode (questions, solutions, hints, etc.)

[Koz]

I'm thinking of buying the game but I have a few quick questions before I do:

1. Are there different maps, or is it basically the same map everytime and you just run through the same game with different characters? If there is only one map to play, how long does it last before it's completed?

2. Do you get to upgrade your units (ala Heroes of Might and Magic or the Disciples series)? If the units upgrade, how is it done (through skills, new buildings, etc)?

Thanks for any answers.

Koz