Shell Programming and Scripting

I want to add lines in my script dynamically.
My script:
...
echo addscript
end addscript
...

Lines to add: (can be put in a file and can be added)
cp /opt/script1.sh opt/script1_org.sh
sed 's/testusr/'${FUNCTID}'/g' /opt/script1.sh > ./tmpfile
mv ./tmpfile /opt/script1.sh
/opt/script1.sh

Actually, I tried and found
sed 's/echo addscript/echo addscript\n\/opt\/script1.sh/' "$fileB" > tmpfile
can add one line. But not able to add multiple lines. I don't want to put \n and do it as if there is a long path for the script directory, it will be pain.

Please help

Thanks
Chiru

Code:

sed "/echo addscript/r script1.sh" file