You can do the water change now--water changes do more than remove ammonia and nitrate. They replace trace elements that are lost to biological processes, stabilize pH, and remove toxins that are present but difficult to test for by hobbyists. So, yep, go ahead.
For the fines--I like having them in the tank. By volume, smaller particles provide more surface area for bacteria to colonize than larger particles. So--I wouldn't worry about removing them. They don't harmanything, and as they are increasingly colonized by bacteria and microfauna, they won't be prone to clouding the tank if disturbed.
For the fines--I like having them in the tank. By volume, smaller particles provide more surface area for bacteria to colonize than larger particles. So--I wouldn't worry about removing them. They don't harmanything, and as they are increasingly colonized by bacteria and microfauna, they won't be prone to clouding the tank if disturbed.