How to convert unix command into Awk statement

Hi all,

How can i use the below unix command in AWK . Can any one please suggest me how i can use.

sed -e "s/which first.sh/which \$0/g" $shell > $shell.sal

where $0=current program name(say current.sh)
$shell=second.sh

awk "{ gsub (\"which first\.sh\", \"which $0\") } 1" $shell >$shell.sai