I haven't flown UA in a couple of years, and the last time I did was way before I was a frequent upgrader.

I will soon (9/29) be on UA 947 IAD-LAX, booked in D; it seems that it is a three-class 777 with international configuration. Do they have sleeper seats in first class? Is it worth to try to get an upgrade, which apparently would be 15k LH miles? Or is the difference to C not that much?