elm tree

I recently acquired this really nice and very old hokkaido elm. I won it during an auction at my local bonsai society club meeting. I cleaned it out a bit to gain some semblance of shape and to remove some structural issues. I understand how brittle these can be so I anticipate it will...

I recently purchased an elm bonsai. It came in a plastic pot with what seems to be regular soil. Should I replace the soil or wait till spring? An image of the soil is attached

Its budding well after its fall out of its pot, Here is a better image of it with a proper camera. Next plan is to plan what needs to go next spring :-)