Does an Ipod under one year warranty with cracked get free screen replacement

No, accidental damage like a broken screen is not covered by the warranty.

Apple will exchange your iPod for a refurbished one for $199 for the 64 GB on and $99 for the others. They do not fix yours.

Apple - iPod Repair price

A third-party place like the following maybe less. Google for more.

iPhone Repair, Service & Parts: iPod Touch, iPad, MacBook Pro Screens

Replace the screen yourself if you are up to it

iPod Touch Repair – iFixit

No, you can do an out-of-warranty replacement for a fixed fee or find a 3rd party repair site that will just fix the screen. A warranty covers manufacturer's defects not accidental damage.