Gst small service provider

SIR ,I AM A SERVICE PROVIDER AND THE RECEIPTS FOR EARLIER FINANCIAL YEAR IS LESS THAN 10 LAKHS , POST TO IMPLEMENTATION OF GST IF IN CASE IF I OPT FOR REGISTRATION THEN WHETHER I HAVE TO COLLECT SERVICE TAX OR NOT AND IF IN CASE I COLLECT SERVICE TAX ON BILL THEN I WOULD BE LIABLE TO PAY TAX TO GOVERMENT BEING COLLECTION IS MADE ON THE PART OF GST FURTHERLY IF I DONT GET MYSELF REGISTERED THEN MY CLIENT WOULD BE LIABLE TO PAY GST PLEASE PROVIDE MY GUIDANCE FOR THE SAME