I have need to do work around skylights located in vaulted ceilings, and also windows around the same height.
What is the best tool to reach this height? What type/size ladder? Also, is it possible to use a aerial lift for this?
Depends, what is the access to the area like and what is in the area itself?
Lifts tend to be larger than what will fit inside a house, they are also very heavy which can cause problems with the floor. A lift would be perfect for a warehouse situation.
Inside a house, especially a furnished one, scaffold would be the better choice.
A good tall step ladder can be handy. Just get one tall enough so you don't have to use the last step.
For a large or involved job, scaffolding might be best.