Noob question from a newbie

I'm planning to build a theremin based on the schematic I've seen at, but I have a couple of questions (I have no knowledge of electronics, but I'll have someone helping, but I need just a few tidbits of info)

http://www.thereminworld.com/files/projects/handdrawn/handsch.gif

Firstly, the diodes on the schematics: can I use any type of diode, or is there a specific one I should look for?

And for the coils (apparently those are nasty, so, if you guys may, I'd like you to go into as much detail as you can), how would I go about making them, in terms of material of the wire/number of spires/diameter of the spires, etc? There are a lot of coils, so messing up would be, well, bad.

And, as for an on/off switch, I don't see one there (could be the lack of knowledge, but I don't know), so how would I go about putting one?

Sorry to ask so many questions, and huge thanks to whomever helps.

Coils are not nasty, unless they're toroidal and you have to wind 'em yourself :-)

This:

http://www.oldtemecula.com/theremin/ultimate2b/boxwinder.htm

May help with the coils...

Canopus, I don;t have any help to offer you but if you could keep us posted on your progress we would appreciate it.

There are a few of us who want to "roll their own" but haven't taken that plunge yet.

Alright, I'll post how it goes, though it will probably take me some time to start, since I'll only have access to materials and stuff by march. I hope I can find some more info on it before I start, since even though I'll have help, it's nice to know as much as possible.

Also, thanks for the link, Ardor.