Isn't it nice, the things that POs do? I had a bathroom full of clear silicone when I purchased my '72 Overlander. (In prepping for refinishing, that took the longest, just removing all of the silicone.)
If you have all the pieces to the vanity, you could repair in with fiberglass. I have had success with using Bondo Fiberglass Repair Kit (around $10) repairing the abs fixtures. I just finished repairing a
crack in the rear end cap of my '73 Sovereign, using fiberglass on the backside (I didn't take a photo when it was out) and filling in the front crack with 2-part marine epoxy (loctite). Once sanded smooth and painted, the crack was
gone.
If you're up to it, take it all
apart and refinish the
pieces and your bathroom can look like
this &
this . (or
this &
this)
Do you have a pic of the vanity?