Unfortunately, the machines are either totally beat up, or they have been restored and are extremely costly. For those of us willing to try, the best thing to do is to purchase a beat up game and restore it.
I purchased a fairly beat up machine that had some electrical problems and the playfield was worn through, so I needed a replacement playfield.
There appears to be one current source of playfield overlays: ClassicArcades. There used to be several sources for pinball playfield overlays: Fabulous Fantasies (which has one? overlay available), Phoenix Arcade (none anymore), Arcade Shop (one available), and Classic Arcade Grifix. (Arcade Grafix seems to have gone out of business).
However, most of these seem to have stopped making overlays. Small private shops maybe the best source now.
Once you have selected the source of your supplies, the next question is how to accomplish the restoration?
I supported my playfield to two saw horses, on the top and bottom of the field. This is tricky, since a small movement of the playfield can send it crashing to the floor. Plus sag can be a problem once the wood edging is removed. You may want to consider building a frame to support the playfield on all four sides.
Unplug all of the electrical connection from the playfield and remove it from the machine. Get a second person to help you. Place it on the supports you set in place on the previous step.
Next, get a digital camera and take pictures, pictures and more pictures. If you think you have taken enough, take more.
Before you do anything, take close ups of the entire playfield. Then, remove the plastics and take a second round of pictures. Finally, take pictures of the stripped playfield.
After you have removed the plastics, the tricky part starts. It is easy to dismantle. It is much harder to put it back together. I would suggest that you do two things: 1) get a copy of the playfield locations from the service manual, and 2) get lots of tracing paper and tape it together so it is large enough to cover the playfield.
In EBD, there are four different types of screws (machine, wood, machine with screw top, wood with screw top). Additionally, there are two different plastic posts (two heights). It is important to know where they go! Make notes on the copy of the playfield locations. If you cannot get a copy, then draw one!