I see no problem using ceramics for decoupling high frequencies. Since I do not expect you to be sending control signals to this thing that measure in the low microsecond range, any cheap small signal NPN transistor should do, even the venerable 2N2222.
As far as diodes go, I have always been partial to the 1N400x family. They are cheap and rated at 1 amp. If I recall correctly, the 1N4004 has a PIV of 400 or 500 volts. They used to be available at Radio Shack for something like a dime a piece.