Lifting the door might cause more trouble than it will save you. Or screw up your back.
Use what the pros use. Get two Richardson pry bars at your hardware store. Use one to lift the door and the other one to pry the wheels back onto the wheel guide. You may need to lower the upper wheel guides to allow the door to be lifted. The adjustment is a philips screw on the front and back of the door. Inspect the bottom wheels for damage, they sometimes break in half. DO NOT stick your fingers under the door! You will learn the Himalayan scream dance in a hurry.
To perfect ease of operation use STP silicone lubricant on the sliding surfaces.