Welcome to APUG..

In a previous life (when I was a camera technician) I repaired a couple...it's one of the easiest 58mm/1.2 lenses I've repaired....especially compared to something like a Canon R sereies 58/1.2...

Would I recommend tackling the repair? Only if you have cleaned the diaphragm blades on several lenses in the past, and are comfortable dismantling lenses..

The lens shouldn't present much of a problem to an old camera technician - someone who has been in the repair business for say 20+ years...

I'd happily service it for you - except that I'm in Australia, and the postal service between our 2 countries can at best be described as terrible.....

To be honest whether you would/should buy it depends on how much he wants for the lens.....have a look at what they've sold for on ebay in the past, and if you can get it for half that price then it's worth considering...

They are a great lens (I've owned a couple). From personal experience I think you need to ask yourself one question - are you ever going to stop it down past full aperture??

Cheers

Andrew