Thank you for all your reply.
Bill Rouse's pre-purchase consulting package seems like an amazing idea. Unfortunately it seems like he is no longer offering this service for Amel's older than 1988 (please correct me if I'm wrong).
Here is a link to a photo album with photos of the maramu. A mixed bag of photos we took during our first visit and the photos provided by the broker.
https://photos.app.goo.gl/vRXr1HNfMZGYdULH6

And here is the listing from the broker (in French though):
https://www.annoncesbateau.com/bateau/1981-amel-maramu-5016467/

What I could see is the following:
the lining inside is coming unglue in places (aesthetic)
the gooseneck of the mizzen is coming loose (critical)
the varnish near ONE window is pilling off (aesthetic)
I was wondering about the bolts for the winch and the stoppers showing up on top of the lining 
The engine has nearly 7000h and is original 

Couldn't find much else to complain about but I didn't take everything apart either.. planning on doing that during the next visit (which is now scheduled for Saturday).

I also know that in 2000 it went trough an extensive anti-osmosis treatment from a professional company (traitement curatif par pelage du gelcoat ... pealing of the gelcoat?)
In 2010, the mast was removed to fix an issue of electrolysis at the bottom of the mast (between the mast and the deck of the boat)
The in-mast furling was added in 2004
Fridge replaced in 2003
One blackwater tank added in 2010

That's about all I know at this stage.
Cheers,
Ben