I want it to rotate at X° and stay there, basicaly, as a servo. Is it possible? If, yes, how ?
Correct me if I'm wrong, but a continuous servo doesn't know at what angle it is, but it can rotate as a motor.
What you have said is right. For feed back, I would purchase a stepper with an encoder on it.
Though some of the hall effect encoder chips are reasonable low-resolution absolute encoders. Surface mount though, and you need a particular magnet for them
Here is an example of a cheap motor and encoder.
However, it will not program exactly like a hobby servo but can be programmed to behave like one.