I think transfering from Microstrip to CPW will be quite straight-forward. You may just need have the following layout
Top View
--------------------------
microstrip ground |
|\\o\\\\\\\\\\\\\\\\\\ CPW ground
|---------------------
|
----------------------------------------
\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ CPW Ctr Conductor
----------------------------------------
|
|---------------------
|\\o\\\\\\\\\\\\\\\\\\ CPW ground
microstrip ground |
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You need to have some vias to connect the CPW ground to the microstrip ground underneath. Also, you may need to optimize the dimensions for good matching.
Regards.