I'm new to owning locos with dual-mode decoders and today I rushed home from the hobby store and put my beautiful new 2-6-0 on my partially-built layout, fired up the cheapi train power 1300 power pack.  Mystified by the flashing lights and jerky operation, and assuming that, as with old fashioned DC locos it just needed more juice, I floored it. All it did then was flash its lights and make pathetic snapping sounds
THEN I consulted the little guide that came with it and realized I probably fried the decoder.
1.  Did I?
2.  If so, how do I get a new decoder and replace it?  Is it easy?

Yes I know I should have read the guide first - won't make THAT mistake again!