Poor mans shift kit? I think not! After re-reading your first post, and reading your Q about why would someone would plug the vacuum port, I came to this conclusion.
First of all, I can't see 5 qts. of tranny fluid "seeping" out of a dipstick hole on the tranny unless you had it parked sideways on a 45* hill, and even then.... 5 qts?
I think the shop that did your work either, does real shoddy work or, tried to set you up for a new tranny.
I sure wouldn't let them work on my brakes!
Glad to hear it's runnin'