> 1.  Is the suggested 100R a current limiter between the buffer
> output and LED or something else?

The idea is to split the power supply into two mostly independent
Vcc's. This isolates the PIC from any droops or spikes that may
occur in the LED section. Not perhaps quite so necessary in a
setup that is powered by a low impedance mains PSU, but in
battery supplies it can make a difference. The reason being that
as batteries discharge their impedance goes up and they can't
supply a lot of instantaneous current as when fresh. Any demand
in one part of the circuit could cause unwanted Vcc drooping in
another part of the circuit. By isolating various parts and storing
charges in large caps this can be minimised

PIC  <  Vcc >  LED IC

"Vcc" here is where the 5V comes in and is split in two - the PIC
gets its power through R or D and the LED IC through a D, and
each side has a storage cap

> 2.  Why are there two filter caps on the PIC power pin instead of
> just one? Are they in series or parallel and why not just substitute
> the equivalent value?

Well, good luck finding a 100.1uF cap ;-)  The large electrolytic acts
as a reservoir cap, the smaller (preferably ceramic) reacts to faster
events like spikes from switching demands

This page here has just about anything basic you'd want to know
about the many different types of capacitors

http://www.uoguelph.ca/~antoon/gadgets/caps/caps.html

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