How often should syntetic oil be changed I've heard that it is safe to change every 12k and oil filter should be changed every 3000 miles in between

I recommend changing synthetic oil and premium filter (e.g. Mobil 1 EP, Amsoil Ea, or Purolator PureOne) every 6,000 miles or 6 months, whichever comes first. With extended drain intervals, I recommend that you perform regular used oil analysis (UOA). This allows you to know exactly where you stand.

In addition to TxGreaseMonkey's advice, make sure you use a premium filter that's rated for extended life. MOST cheap filters are NOT. Read this article on economy versus premium filters.

Economy versus Premium Oil Filters