Skipping sensation- what you are feeling could also be as simple as the rear deraileur not being centered over a cog. The bike will try to "shift" when you stand on the pedals and that can feel like "skip skip skip". This may be remedied by adjusting the shifter, assuming it is the friction type...meaning it does not "index" (go click click) to each gear. However, it could also mean the deraileur is bent, but you are going to ditch it for SS anyway.

Point is that the crank may not require replacing which will keep your cost down.