HI
currently all is perfect and i dont want to screw things up.
can i install curl by doing
"sudo apt-get install php5-curl" then
"restart apache"?
will clients then be able to use curl functionaries if their script requires it. (eg. owncloud)
thanks
aptitude install curl php5-curl
normally no restart needed, after installing cURL 
If you want to use the php curl extention, you should
Not with a bridge like php-fpm. Then it should be enough just to restart the php service, but this should happens automatically after installing a new extention.. 