Changing Prices from Gold to Silver
 

I would like for my custom campaign to use silver as the standard for coinage instead of gold. Thus, a trusty longsword would cost 15 sp, as opposed to the 15gp cost listed in the book and application.

Is there a way to do this all at once, or do I just need to let people handle this outside of HeroLab?

No easy way to handle this that I can think of. If 15gp is exactly the same as 15sp it would be better and easier to most likely track this outside of the game. Especially if its 1:1 you can just enter into HL the players sp as gp and any lefter over sp becomes copper I assume.