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WAS:
The bus shuddered as it changed gears, hastening to the city on the horizon: Topeka, Kevin’s hometown-to-be.
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Is that too confusing for an opening line? How about the employment of the 'as' and the colon?

Part of the problem is the "it changed gears, hastening..." bit. There's a couple of issues with that, actually. I suppose it's fair that the bus has an automatic transmission and therefore can change gears without the driver making it happen. But the question is: Do I need to know the bus changes gears and shudders while it hastens to Topeka all in the same sentence? Probably not. Another issue is that it might be read that the gears are hastening and not the bus. You don't mean that, but it could be read that way. Putting a conjunction ("and") after the comma would separate the clauses effectively, I think. That's my style pref, however -- people will differ in opinion.

More importantly, could the sentence be simpler for the same effect you seek? I would also recommend giving Kevin a more active role in that sentence, if possible. Presumably, Kevin is driving the bus...? If he's a passenger, then perhaps that should be clearer from the get-go. Hard to say with what's there. I don't have a clear picture of what Kevin is doing (though I probably will after this sentence). I can see the bus shuddering well enough, though I don't know what kind of bus it is. School bus? Greyhound maybe? Mid 60's VW Bus with a giant peace sign painted on the side?

Really, I would suggest not cramming in the entire setup in one setence. Take enough time to develop the setting and the character properly. Even if it requires two or three sentences. I'll take clarity any day over a sentence that tries too hard.

For instance, making some large assumptions of your intent, my preference would be to start off with:

Kevin drove the bus towards the city on the horizon: Topeka.

Then I'd develop the bus shuddering, why he's going to Topeka (new home) and so on.

Generally speaking, the goal of a sentence is to cover one thing, preferably very well. Just like the goal of a paragraph covers a particular group of things that are related -- a theme, if you will. Sentences work best when they are simple; paragraphs work best when they focus on one theme. Though a complex (or compound) sentence is mighty handy at times, too. When in doubt, simplify.

The last few weeks I've been so busy at work and at home, haven't written much, and it shows.

I'd almost say that the creative juices in the collective unconciousness are being diverted by all the folks doing NanoNano, if I believed in such a thing.