Session map & javascript

I have a select box which lists instructors full names (from a session
variable: session.eligibleInstructor, created in the LoginController
from a query of a view that returns fullname and email, so
session.eligibleInstructors.FULLNAME returns the fullname and
session.eligibleInstructors.EMAIL returns the email, session.eligible
Instructors returns both:

def eligibleInstructors = dbConnection.rows("select FULLNAME, EMAIL
from zV_eligibleInstructors ORDER BY LASTNAME")
println(eligibleInstructors)
[[FULLNAME:Berg, Douglas, EMAIL:bergd@nit.edu], [FULLNAME:Askov,
Michael, EMAIL:askovm@nit.edu], [FULLNAME:Abba, Jasmine,
EMAIL:abbaj@nit.edu], ...


I want to update a textfield with the selected instructors email
address when the instructor is selected in the selectbox. I know my
javascript is capturing the selected instructor (because I did an
"alert"):

$('#inst2Select').change(function(event){
$('#emailInst2').load('/edu.wit.nonac/nonAcadCourse/create/updateSelect',
{
selectedInst: $(event.target).val()
},
function() {alert($(event.target).val())
}

but my controller action (updateSelect) is not doing anything:

def updateSelect = {

println("UpdateSelect reached")

println("Params: " + params.any())
def selectedInstEmail = dbConnection.firstRow("select EMAIL
from zV_eligibleInstructors where FIRSTNAME=?",
[params.selectedInst])
println(selectedInstEmail)
render selectedInstEmail


}

I have tried multiple ajax-type callbacks , even a remoteFunction in
the "onchange"event. I realize I should haven't to go back to the
database to get the selected Instructors email because it's already
avilable in the session variable eligibleInstructors, but how do I
access the EMAIL value using the FULLNAME as the key? Do I even need
to use Ajax for this? What is the "best practice? I have looked at
hundreds of webpages for the answer but none seems to quite touch on
this exact issue. Even if I could just get the controller action to
fire, that would be a huge step forward. Do you have any suggestion on
how to achieve this? Any suggestions will be greatly appreciated.