I just wanted to post an update for anyone who's interested.
Mom finally got (and shared) an update.
The surgery ended up getting pushed to last Thursday due to the anesthesiologist needing to do more research on Marfans. And apparently my cousin's Marfans variant is particularly rare (not connective tissue degradation, but bone instead).
Anyway, they managed the surgery... managed to accomplish it 'keyhole' (rather than slicing him open from hip to hip), and he was sitting up 2 days later. He seems to be recovering well (but it's hard to say for sure, because he's the type who tends to hide pain a lot). They're still monitoring him to see if this has resolved the particular abdominal pain issues he was having.
I really need to save my pennies and get back to see him soon. He's my favourite cousin... he's not that much older than me... but he has deteriorated so much over the time since I last saw him that he can't even walk much any more, and I'm afraid that he might not be here in 5 years
Breaks my heart.