How do I convert this analog PID to a digital one?
I think that the Type III Compensator you refer, is the one with 3 poles and 2 zeros (3p2z) used to stabilize a voltage mode buck converter. You do not describe the relationship between the loop execution frequency and switching freq. ("1 by 1" or "1 out of n"). I believe that Fbw = 60 kHz is very high to be handled with a  PIC-18F - it would be more consistent with a DSP or DSC. 

In order to be conservative: 


To avoid aliasing Fs > 2 Fbw. In practice: Sampling frequency should be 10 to 30 times the bandwidth freq. 
Another equivalent choice: T &lt; 0.1 Tr, where Tr is the rise time of the 
open-loop system.
The phase shift (degrees) in a given freq. F is -360FT. Since the ZOH (Zero Order Holder) contributes with a T/2 delay, the shift is -180F/Fs. Resulting in -180 deg. when F = Fs. So, for a stable design, pick a low T.
In other hand, a very high Fs can lead to precision errors in a fixed point implementation: Remember that, with a very small T, the poles in z domain tend to unity, since 
$$z = e^{Ts}$$ resulting in very similar values, such as 0.999 and 0.99.