Trading Allowance hobby business - second government gateway ID?

Hello, I work full time and have a government gateway id for that paye job. I also have a hobby business that is unlikely to be close to the trading allowance of £1,000 in this financial year, but I have sold more than 30 low-value items. The BBC breakfast news this morning indicated that if an on-line seller sells more than 30 items, the details of my hobby business will be passed to HMRC. Do I need to register for self-assessment? If so, are there step by step guides available? Do I need a second government gateway ID? How not, then how do I change that ID to a non-work email address? If you reply, please direct me to the relevant paragraphs in the guidance so I can retain them for future reference. Thank you

Hi

As long as you are selling your 'old stuff' and not trading as a business, to make a profit, then there is nothing you need to do.  
If you are trading as a business and your turnover exceeds £1000.00, you will need to register for self assessment, as self employed, using your goverment gateway user ID and password.  
Your existing government gateway user ID and password allows you to access HMRC onlne services (HMRC online services: sign in or set up an account)
or things like your personal or business tax account, Self Assessment, Corporation Tax, PAYE for employers and VAT.

Thank you