Shell Programming and Scripting

Hi,
I just started looking into various aspect of unix shell scripting. I am completely new to the world of UNIX. Could any one help me in solving the following requirement.

I have a parameter file with some data e.g.
sample.param
-------------
Andrew=201
Bob=219
Shelly=239
Student_219=/dir1/stud.txt
Student_240=/dir1/stud2.txt

Now I need to write a shell script i.e. testStud.sh which will satisfy the following requirement:
1. I'll pass a string as an argument while running the script.
2. The script will search the string in sample.param file as a key and return the value for that key. if it's not present in the param file, it'll exit out of the program displaying appropriate message.
3.Now the value returned will be appended to the string "Student_" and the resultant string will be searched as akey in the param file and the value corresponding to this key will be returned.

To explain the requirement in a broader way... let's take an example. Let's say the user runs the script as ./testStud.sh Bob
Now value corresponding to the argument i.e. key "Bob" in param file is "219". Now "219" will be appended to "Student_" and the resulltant string is "Student_219". Now again this key will be searched in the param file and the final result will be the value "/dir1/stud.txt"

Again let's say some one runs the script as ./testStud.sh Roger
Now since there is no key named "Roger" in the param file, it'll exit out of the program with a message "key not found".
Could any one kindly provide me the shell script for testStud.sh?

Is this for a homework assignment?

What have you tried?
What issues are you facing?

Ya, actually it's a small part of the whole requirement.
I tried to solve it, but the output that I'm getting is not perfect. Here is the script that I've come up with:

#!/bin/sh
arg_1=$1
echo "arg passed by user is:${arg_1}"
res=$(awk -F= -v name=${arg_1} '$1 == name {value=$2;exit} END { print (value)?value:"not found"}' sample.param)
echo "mapping is $res"
if [ "${res}" = "not found" ]; then
echo "key not found"
help
exit 1
fi

key=Student_${res}
echo "key:${key}:"
param_file=`grep '${key}=' sample.param | awk -F"=" '{print $2}'`
echo "param file is:${param_file}"

---------------------------------------------------------

But the output is not coming properly especially the last result i.e. the value of "param_file" variable which is displayed as blank though the value is present in the param file.

Now since you have done something, it feels good to guide you.
1) May be help you want to write later...
2) remove the quotes from '${key}=' and make it just ${key}