By everything I've read, and my own experience thus far, the M119 V-8 engine is nearly bulletproof. Yes, virtually every service is a bit more expensive for the 119 compared to the inline 6 -- 8 spark plugs instead of 6, etc -- and even some unsuspected things like replacing the starter is more challenging because of the physical size of the engine. Overall, though, I really like the power of the M119 and with good maintenance (e.g., very regular oil changes) should go a long, long time.
Did you look carefully at the service records? That's a must, in my book.