I think I could tolerate under the hood. dealer said watch for water seepage in trunks. The manuals were in there when I bought and have water marks. Found good used ones for round 100$ on ebay but wrong colors. Found nice silver one but rt side....
So found new part guys on ebay called LABUR parts. looks like parting out exotics. Had the silver mirror I need with small scratch on body but no damage to base for 100$. Just got via fredex. so took apart to swap my mirror to the new base to get clean assy. came from 05 with 42K but no alum damage. If anyone needs advise on mirror assy I may help. just a little tricky in routing the wire bundle.
so when I swapped mirror bases I noticed it looks like the corrosion starts in that fwd small bay and comes up and fwd on base. I think they never treated these correctly. So if moisture rests in there you done. My solution ids to drill small hole in back outboard corner of that area as a drain. you cant see hole
unless you look underneath. maybe treat with alodine if so inclined but should stop rust if you don't have already.
It's not rust. It's aluminum corrosion caused by salt. Salt is highly corrosive to aluminium. Salt and coastal breezes are your enemy. Water actually helps the situation, in my opinion. My parking space faces south and we get a seabreeze, so after 1 year the whole driver side got it - the mirror, doors, left side of trunk, etc. Only on the left side bc of the wind. There isn't a reliable way of preventing it (although I've never seen it on the first-gen NSX). All the aluminum panel Ferraris and McLarens have the issue as well, even fairly current models.