Yizzah, you fell in the common trap of bringing somebody else's discarded bike with all the reasons they sold it. Any and every bike should be ridden extensively and serviced as needed so it is ready for a troublefree week of use.
Perhaps you paid quite a bit for a Craigslist bike, while an other burner might have got one for $2,- at a thrift shop. But that makes little difference. Either way, it's an unfamiliar bike with unknown issues.
So THAT's one definition of the ideal Playa bike: one that you have ridden enough to have the bugs worked out of it.
Regarding the long term effects of the Playa dust... it seems that different people have very different experiences with that. A classic case of "Your Milage May Vary"!
Perhaps most importantly, we all have our own standards for what we consider normal wear and tear, and for what we consider normal maintenance. To say nothing of how we use our bikes!
Bring a bike home straight from the Playa and just set it outside in the back yard until next year, and it will be unridable.
But clean it off, oil the bearings and the chain, and keep it out of rain and fog, and it will be fine.
See you on the Playa!