I'd actually suggest not buying this single, since Billy Liar and Los Angeles are the same recordings as on Her Majesty (which you should also buy), and instead buying the fourth (and maybe third?) track on iTunes.
I can't say enough good things about the first two tracks. Billy Liar is truly one of the Decemberists' best songs-- the beat, the harmony, melody, lyrics-- it's all superb. Los Angeles, I'm Yours, a song reflecting the narrator's ambivalence about the city of angels (mostly how disgusted and intoxicated it makes him feel, probably accurate) is also quite good.
Sunshine, unique to this single, isn't great. It's okay, I mean, just not very interesting. The way the verses are structured and the loud, abrasive drumset makes it sound very fractured. The melody and harmony are fairly weak as well. I might rate it three stars, though, I'm not sure. It's listenable.
"Everything I try to do" is excellent. Amazing lyrics, develops quite nicely, nice instrumentation. I got this on iTunes separately, though... hmm.