Well, MD5 with the letters is hex (base 16), so converting them should be easy, but you will have to use the symbols 0-9 and A-V where:

0-9 are the same, and:
A - 11
B - 12 
...
V - 31
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I can't, off the top of my head tell you the proceedure, but you could lookup converting to hexadecimal, and go from there.

It would be just as easily to convert from the 128 bit string (1's and 0's) to base32 as well.