I am working on an application (new to wM development), and was given the task to write a customized generic framework package around the standard webMethods errors (pub.flow.getLastError). This package will decide to do retries or not, and send back to those consuming our webService a readable soap message. Any ideas and reccomendations will be greatly appreciated.

You also need look into the Event handler services which actually provides the detail exception information to getLastError svc behind the scenes.

pub.event folder svcs.

Also this Advantage document provides you list of standard error types/message:
"webMethods Error Message Reference 6.5 and 6.5.1.pdf" (Cross-Product Documentation section)

This could help you as a starting point.

HTH,
RMG

Thanks. Do you know if there is a similar document for 7.1.2

It will be the same document applies for 7.1 also.There is no specific document to 7.1.2 released.

HTH,
RMg