I speak Sardo, and I studied Latin for 5 years at High School, and I was very bad at it.

So I would say that "modern" Sardo (defining the "old" as the first written texts some centuries ago) it's close enough to Latin to see where every word comes from, but definitely too far to give you understanding.

I can understand Spanish though :) (context: we've been in the Spanish Kingdom for like 400 years, and the language have been influenced a lot, many shared words.)