Wheels are easy to remove, just check brake clearance, pop the QR, and it should pull out. Re-installing the wheel, be sure the axle is securely seated in the fork, and tighten the QR. Spin the wheel to make sure there is no brake pad interference. My disc brakes are TRP mechanical and have spring loaded pads, so I just pop the wheel out, never heard of using a spacer or pad block. To release the QR, you may need to rotate the lever counter clockwise on the axle a few turns to release ftom the fork, turn clockwise to re-install and tighten the QR. After one time it will become second nature.