As first reported last fall, Sony is letting folks change their PSN names through their PS4 or web browser. The rollout out will happen later today.
Below is a simple walk-through to explain the process.
So, the first change is free, but additional changes will cost $10 each time (or $5 for PlayStation Plus members). However, not all PS4/PS3/Vita games will support the new IDs.
For those with further questions, Sony also posted a FAQ for players who are thinking about changing their PSN Names.