I don't know much about organic chemistry, but amino acids are fairly simple molecules, and if memory serves they've been found free-floating in molecular clouds. I'd tentatively bet at 100:1 odds that that the right isomers of at least the simpler ones will be found conditional on the experiment being run, since a comet's basically a giant slushball of compounds left over from those molecular clouds.

On the other hand, I'd put the odds at well under 1% that we'll see terrestrial-like isomer ratios. That would be tantamount to finding a biosphere -- an active one, not just the remains of one, since amino acids are photosensitive and tend toward an equilibrium isomer ratio unless biological processes are leaning on it.