I'm not a Guru , I do like Garage Band and use it every so often ….
a couple of things off the top of my head ….
getting midi out of GB is almost a waste of time because its a locked DAW
haven said that
the easiest way I know how to get midi out of G B is to open the G B project up in Logic ,
once in Logic merge all the individual clips so each midi track is one continuous track …
if you don't merge them , each separate loop / GB grove clip is gonna end up with it's own track

when you export the project as a midi file ….
if you don't have access to Logic to open the GB project up in to grab the midi and export as midi , you can still get very decent results by working with the audio end of GB in your DAW of choice
a lot of people don't know that GB can do 32 bit audio exports

it's called track lock and it is hidden in plain sight ...
here's a link to access and grab 32 bit audio out of GB ...
I know its not the original topic ,
but if you have a thing happening in GB , you will be able to put it in the DAW of your choice as a high rez audio file
I've used this approach many times …..before I got Logic , and it works very good
http://www.delora.com/tips_and_trends/export_garageband/export_garageband.html hope this helps ,
Kenny