Shell Programming and Scripting

I'm in an introduction to Unix class and well I'm kind of stuck on one part of the lab for this week or shell scripts. Basically we're given a file named address.data and we're supposed to create a script to sort it according to zip code, last name, and first name (not at the same time of course). The guidelines for the finished script is:

1. Ask the user for the name of the data file.
2. Verify that the file exists and is readable.
3. If the file does not exist or is not readable, issue an error message and exit.
4. Sort the input file according to the instructions given above.
5. Use awk to print the sorted file according to the instructions given above.


Now I'm having trouble getting the user input to be verified since when I input address.data none of the echos display and it jumps to my case. The case doesn't send anything to the awk so that comes up blank as well but when I run a separate sh without the user input part as ./address.sh address.data the case works fine and sends the information to awk and it's displayed correctly. So my question is how do I get the user's input to work correctly at the start and to pass the data to the awk. Any ideas? My scripts are below.. and please excuse the lengthy post.

sortaddress.sh
#!/bin/sh
#
# This script was written by .
# The purpose of this script is to sort a
# file containing a single line address
# by the zip code, last name, and first
# name and then format it properly.
#
echo "Please enter a file to sort: \c"
read filename

for file in $2
do
if test -f $file
then
echo "$file is a file."
else
echo "$file is not a file."
fi
if test -r $file
then
echo "$file is readable"
else
echo "$file is not readable."
fi
done

echo "Please enter one of four of the follow selections:\n"
echo "1 to sort by zip code."
echo "2 to sort by last name."
echo "3 to sort by first name."
read choice

case $choice in
1) sort -k8 $1 | nawk -f sortadd.awk
exit;;
2) sort -k1 $1 | nawk -f sortadd.awk
exit;;
3) sort -k2 $1 | nawk -f sortadd.awk
exit;;
*) echo "Please enter a valid choice."
esac

sortadd.awk
BEGIN {
printf ("Your desired address sort is as follows: \n\n")
}

{
print $2 " " $1 " \n" $3 " " $4 " " $5 " \n" $6 " "$7 " " $8 " " $9 " \n\n"
}