I have a "Sample" Funhouse version that was not a Diamond Plated version, it was a mylared version.
However, the mylar wore out in a few places and when removed, it left a lot of glue residue that is hard to get entirely off.

So, I'm considering replacing the rare sample funhouse playfield with a remake funhouse playfield. Does the PF replacement ruin or decrease the original sample version's value? I personally don't put much weight in the sample collector's value. Am I doing something I will regret? The cabinet is also faded and needs decals.

Hmmm... That's a good point as the Funhouse boards are actually different than the regular/standard run version. For example, I cannot use the updated sound or cpu ROMs.

I'm not entirely sure about the differences in the actual playfield, if any. I better check, or does anyone know?

No, the sample Funhouse did not have an extra STEPS target, at least mine does not. The serial number on my FH designates it as a later run sample version.

I tried the 91% isopropyl alcohol, flour and credit card scrapping method and ended up using my thumb for most of the removal and had painful blisters for week. However, it was only 50% effective in removing the darn glue residue. As a result, the glue residue is thinner, but still present on most of the main playfield area. Especially difficult are the glue residue over the inserts in the clock area. I also tried the goo gone and acetone. I have not tried using a hair dryer, good gone and scrapping yet, which I've been told may work better.