No, dont do it!!! I did a similar one when I first got here and it wasnt worth the money. Its SOOOOO easy to do everything yourself AND you save $$$. Dead easy to set up your tax file, bank account, book yourself into a decent hostel for your first week. Most hostels have beach walks organised, city tours, BBQ nights etc so its really easy to meet people.
I used to work for ThaIntro (OzIntro's Thailand equivalent) as it happens and whilst its a great way to meet people they make their money by selling you onward travel at full or even fluctuated prices because by the end of the week the group leader is your 'best mate' and you trust what they say and everyone else is doing the same.
PM me and I can help you sort out your travel arrangements/first weeks accommodation for you x