> 1. Does the code syntax change depending on the crystal speed?

No, only the execution speed changes. But you may have to
alter code that interfaces to external components to suit their
timing requirements, particularly in analogue circuits

> it seems like if it didnt why wouldn't you just always use the fastest
> one, the price differences seem minimal

I'll give you a specific example of why that doesn't always work out

I've got a circuit with 4 x 16F628 on it. One is running at 3.6864MHz
to do serial 19k2 comms to external devices. The other 3 run at
18.432MHz. They have jobs to do that requires speed. However,
the 3.6864 PIC also sends data to the other 3 by simple one-way
bit-banging (a two-wire clock/data system). As it's running at exactly
1/5th of the speed of the others, it means that the fast PICs have
plenty of time to reliably pick up the data without handshaking (which
can take an extra pin / time / code)

> 2. Are there any internet resources that explain more about a
> hexadecimal value crystal vs. a decimal value crystal? I have a
> problem understand how a crystal that emits frequencies would
> have anything to do with binary or decimal, I would like to know
> more about that.

It's not the crystal itself, it's the mathematics of its frequency. If you
wanted instruction cycles (IC) of exactly 1 microsecond, then a 4MHz
crystal is what you want to use. In my example above, 3.6864MHz
is an IC of 1.085us. But absolute timing isn't what I'm after - it's
serial comms timing that matters, and generally externally-set comms
timing (from eg 9600 baud, 19200 baud from a PC) is based on
hexadecimal timing. The 18.432MHz PICs in my example could be
run at 20MHz, but I just happen to have got a load of 18.432MHz
crystals at a clearance price

> 3. Ceramic Resonators, I imagine when you talk about accuracy
> you are referring to the fact that a clock cycle varies in the time
> it execute? so basically this only matters when you need accuracy
> within milliseconds and consistantly correct?

That's about it, although ceramic resonators are normally pretty
close to the marked value and not really that bad. They are more
likely to drift in frequency than crystals though

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