Daize, I am embarassed, you will think I'm giving you the runaround. I'm the one who recommended that you ask your question here. And this is the right place for organizing your garden and gardeners. But as far as soil improvement, you probably also want to check the soil forum. Start with their FAQ on Interbay Mulch. Sorry!!!! (Actually, these guys probably know tons about soil, also.)
Here is a link that might be useful: Soil Forum FAQ on Interbay Mulch