Replace particular character from the string or line

Question

Hi all,
I want to replace the perticular character from the string .
My string is
string original="(My friend name is "WALTERS K,SCHULTHIES SPL ","Lenny")";

Above is my string and i want to remove the comma only is in the first double quote from the string and replace with a single space.
If comma ocuur otherwise in  my string then i want to keep this as it is. No change in the whole string .
then Output that i want is the
(My friend name is "WALTERS K SCHULTHIES SPL ","Lenny")


How i will do it?