For the headlamps the S1 and S2 both used the New Beetle.
However due to the opposite curvature of the body where they were placed a left light on the beetle was a right light on the Aero.
However for most of the rest of the car there were significant differences, wheel, axle, engine, gearbox, brakes, dash, hood, petrol tank positioning all got a big change. The S3 was like an S2 with a facelift and Mini lights.
You should be able to remove the wheel and change them yourself but beware of the very fiddly mounting. I believe the glass is bonded to the unit and thy are one item. Do NOT over tighten the mounts or it peels the lamp body away from the glass front allowing dirty and water to get in and giving it a black eye. I do not have a torque setting I am afraid as I let the dealer do it for me knowing it was a pain.
