Yes, MR16 LED bulbs need a transformer if you are replacing them with Halogen light bulbs. If you do plan on switching out the bulbs, make sure to calculate the maximum load. The transformers maximum load will help you determine which MR16 LED bulb you will need.
Changing an MR16 LED bulb does not require too many steps. However, if you are not a licensed electrician, it is important to hire one to change out the bulbs. Below are the steps the electrician will follow to change the MR16 LED bulb: