Toursit Visa Question

Hi, Ive lived and worked in China for the past 2 years and just returned to Ireland in December.
I am looking to go back to China in February on a tourist L and eventually get another job.

I was just wondering how difficult it will be for me to transfer my tourist L to a work Z.

Will I have to travel to Hong Kong to do this or can I obtain it in china?

Thanks in advance