Actually they should print it at the fixed 2002 price 1 euro:320 drachmas.
Why? By now Greeks are used to the euro pricing, keep it simple and remember that this would be a temporary currency. They'd probably create a new name for it to avoid any confusion with the "old" drachma. How would "temporary drachma" sound in Greek? Or "emergency money"?
If it were to fall only 20-30% it would be good.The fear is that it will fall 300% this means that everyone will make 3 times less deadly for public servants and the middle class.
It would be very volatile for weeks, maybe months but if Argentina is any guide the initial devaluation was in the 20% range. Things got worst before they got better for sure but if Greeks are unhappy with the current measures maybe they should try a new drachma for a while? Very, very quickly most people would realize that the current reforms are not as bad as a new, and quickly devalued Drachma would be.
Also, supposedly there are already plans for printing new bills if needed and it can be done fairly quickly. Both Germany's Bundesbank and Sweden's Riksbank helped the Baltic states and also Croatia and Slovenia (not sure about Ukraine?) to print their new respective banknotes once they became independent. In Estonia's case it went from placing the order, designing and printing money for the whole country in less than 2 weeks. (I'm talking about the first batch of bills).