Just using compost would be too unstable for a berm.* You will need a combination of materials.* Here's how to build a berm.* You can always add 3" to 4" of compost to the top of the soil and mix it in the entire planting area once the berm is constructed.
You can stake your trees for 6 to 12 months.* They will need to sway a bit in the wind to strengthen their roots.
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.