As another commenter said the model number is inside the door, you probably will need to remove screws from the back panel but getting it out of its hole should be relatively easy, most dryers weigh 100lbs max and are pretty easy to manhandle. If you search the model number you can likely find a replacement part online. What does the knob do? If it's the timer the replacement units usually run around $100 USD.
As another commenter said the model number is inside the door, you probably will need to remove screws from the back panel but getting it out of its hole should be relatively easy, most dryers weigh 100lbs max and are pretty easy to manhandle. If you search the model number you can likely find a replacement part online. What does the knob do? If it's the timer the replacement units usually run around $100 USD.