Crystal Radio Tuning Cap

This is very similar to the type of capacitor shown on the plans. It should work about as well as the one shown.

Don't expect much performance out of a simple receiver like this. It has very poor selectivity and depending on where you live will probably pull in two, three or more station on top of each other and no adjustment will be able to separate them. Crystal sets like this come form the early days of radio when there were few stations, usually only one in a given area and cross interference was not a problem.

Crystal sets can be fun to build for the beginner, but because their performance is so poor, one should not spend much money on them. They are usually made from junk, scrounged parts, oatmeal boxes or toilet paper rolls for coils and so on. Don't pay much for anything, you'll be disappointed.

More elaborate sets have more selective filtering and can separate stations a little better, but no simple "tuned RF system" which is what a crystal set is can separate stations on the modern AM band effectively unless you reside out in the middle of nowhere with only one station near by. Look up superhetrodyne.

found a schematic of a very small crystal radio, and would like to

Found a much better one, with more selectivity, which is what I want. Only thing is, part of it is grounded to the front aluminum panel on the authors radio, I don't want an aluminum panel on mine, do I just connect that grounded section to regular ground?

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Yes, If this is a crystal set with no amplification, a good earth gound is important to get sufficient signal. The aluminum panel ground does nothing so don't worry about not having it. You can drive a metal stake several feet into the dirt to get a ground. Modern house wiring normally has a groung rod driven into the soil. It is usually located near the main power panel and can be accessed at an any elecrical outlet on the center terminal. However this ground may be noisy and may introduce hum into your reception. Try it and see. Also, a long wire antenna will be helpful in getting a good signal.

I already have a ground rod, for my regen radio, for an antenna, I use my outdoor TV antenna.

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Actually for AM radio reception, the twin-lead TV antenna wire is acting as the AM antenna and the TV antenna itself isn't adding much if anything.

The 250 pF capacitor will have no practical tuning affect.

The combination of the 2.5 mH choke and the 250 pF capacitor are a gross mismatch. An inductor of around 150 uH would be more appropriate to the frequency band.