Lots of folks clean up at work after a sweaty commute. The fortunate ones have showers at their offices; others clean up pretty nicely in the restroom with the sink and a hairdryer that they keep in their desk. I've done both successfully.

You can always sell your heavy bike and get a lighter one. It's a myth that a heavier bike will make you stronger. A lighter bike will make riding more enjoyable, and so you'll ride more, and then you'll get stronger. Be sure to get a bike that fits properly (a lot more on that throughout these forums--check out New Riders)