[Serdev] Module Assistance - How to modify payload contents.

[Greenwell, Gary L, JR, ALABS]

First - ser-0.9.6 on Linux.  
 
That being said, here is what I would like to do:  
 
On an INVITE, replace the Content-Type: application/SDP with Content-Type: multipart/mixed; boundary=unique-boundary-1
 
Next I want to modify the payload to contain:
 
--unique-boundary-1
Content-Type: application/SDP
*** Original SDP Information ***
--unique-boundary-1
Content-Type: application/ISUP; version=nxv3; base=etsi121
Content-Disposition: signal; handling=optional
*** A Kludged ISUP IAM ***
--unique-boundary-1--
 
Then obviously update the Content-Length to reflect the additional payload. 
 
I am guessing this is achieved by using the data_lump API, but after that I am at a loss.
Any advice would be appreciated.
 
Thanks.