Before spending any dough, take the time to see if you actually have a problem with the existing chainset. Hyperglide or similar cranksets look worn when new, and the cut down or broken teeth might be the shift gates made that way for easier shifting. Then again the rings may be shot.

The best test i whether the chain runs without skipping under load, since that;s what matters. You can also get a sense of the wear by installing the new chain and pulling it away from the sprocket midway of the wrap (3 o'clock). If you can pull it away from the sprocket far enough to see 1/4" of daylight underneath, the ring is well worn, but if not, it's a pass.

As far as replacing the crank goes, odds are you'll need to buy both crank and a bottom bracket because modern cranks take shorter spindles than older ones used to.