The modification of the 600 series camera is fairly simple--a piece of masking tape or neutral density gel over the light sensor usually lengthens the exposure to match the slower Time Zero film, which is better for manipulations. YRMV.

When inserting a film pack, one needs to cover the metal contacts inside the film port. A piece of cardboard torn from the film box does the trick, covering them until the pack is almost completely in place, at which point the cardboard can be removed so the film pack can be fully inserted and the battery will make contact. Seems to me this modification was posted on the the Polaroid website. You'll also find it in Kathleen Thormand Carr's book on manipulated Polaroids.

I prefer the harder to find 680 SE camera, on account of its sonar focus and built in flash, than the trusty SX-70, some models of which have auto focus, but flashes were either flash bars or aftermarket accessories (slow recycle and AA battery hogs).

On the plus side, the SX-70s are easy to find and lower priced.