Hi Wolf!
The best way would be to change the scenario itself and not edit the saved game.
To edit the scenarios you need to download the official AACW database which can be found here:
http://www.ageod-forum.com/showthread.php?t=5358
For example the source file for the 1862 campaign would be
AACW_Setup1862_Campaign_v1.07i.xls. You can open and edit it with MS Excel or the free OpenOffice.
Near the top of the file you will find the command 'ChangeMoneyPool'. This command set the initial availably money (it changes the value from the current one, which is at the beginning zero.)
You can now change the value, save the file, export it via the CSV-Splitter and compile it with the game in Edit Mode. You will find the procedure described in several threads in the modding forum. If you getting stuck just ask again and I will give you a more detailed description.
Cheers
Norbert