Upload & Sell: Off
$350 is a good price for the N Makro-Sonnar. The conversion by Conurus is more expensive than that, at US$619. He's been raising his prices apparently. One of the reasons is that ebay sellers have been buying up all the cheap Contax N lenses and increasing prices for all of Conurus potential costumers.
@Jae: According to the Leitax Contax for Canon page, the C/Y 100/2.8 isn't compatible because the screws are in different locations from the other lenses. The same will be true for the Sony mounts then. It's most probably possible to still do a mount swap if you drill holes in the right places, or have someone do it for you. Jim Buchanan may also be able to do the conversion for you.
@Bif: Leitax provides high quality mount replacements for many different camera and lens mounts. Not really necessary for Canon since there are cheap adapters, but other camera mounts don't have space for adapters due to the longer registry distance, but Leitax mounts solve this problem because they replace the original mount and provide the correct registry disance. See leitax.com.
Anyway, I can fully relate to your experiences with the lens. Many shots that I take with it also make me go "wow".