You might also consider our FLORA
processor. It is in Beta test now. The pads on the FLORA can be either soldered or sewn with conductive thread. To answer some of your other questions:
A. Programming most of the arduino variants is no more difficult than a standard Arduino. There may be minor differences in the number of available analog and digital pins, but otherwise they use the same code.
B. A standard Arduino or Boarduino
are easiest for prototyping with a breadboard. Ladyada's Arduino tutorial
s are an excellent way to get started.
C. This tutorial
shows you how to hook up discrete leds. This will work for experimenting with the colors and quality of light you can expect from RGB leds. But if you are planning to do 20-30, you should really consider an RBG pixel strand. You will not be able to drive that many leds (in serial or in parallel) directly from the Arduino. You will need some additional driver circuitry to handle the current from all those leds.
We have both flat
pixels. The latter are not that much different than a 5mm discrete led by the time you solder leads onto it.
If all leds are going to be changing synchronously to the same color, you could use a drive circuit similar to the one we show for the RGB analog strips. Each led would need its own current limiting resistors, then you could drive them all in parallel with the MOSFETS.