There is no changing plates (unless you would have a government or exonerated plate, these change this year). There is the yearly marbete, of which renewal starts in October, you can change until end of year and pay in three installments.
Then there is the revista, which since years ago was only paying a small tax and you wouldn't need to have your vehicle checked, neither were there any stickers to prove you had the new revista. That changed, you have until December I think to get that done. They check if your vehicle is able to drive, if you have a fire extinguisher, warning sign and first aid kit. Next year they hay they will do thorough checks in a workshop (don't see that happening).