I think I've got it.
1. Treat the characters as numbers from 0-35, where 0-9 is 0-9 and a-z is 10-35. eg, o, the 15th letter is 24.
2. Reverse the numbers, eg, 0 becomes z, 1 becomes y, 2 becomes x, ... a becomes p, b becomes o, ... giving us vumnkrkutnktvuwmtlspwlktzqmpkwlt
3. Add the code string 8rz2mgtvlrqoslizelqw5l5e7v00xgl8 cylically circling. So if we add 1 to z, we get 0. If we add n(23) to q(17) this gives us 5. (23 + 17 = 40 = 5 mod 35).
This gives us 4llp78dpeeahnfel87il27p87lmphc72
4. Reverse the numbers again, eg 0 becomes z, 1 becomes y, 2 becomes x, ... to give us:
weeatsmallpicklestheytastedainty