Greeces owes billions of Euros to the IMF and European Union. What happens to those debts if it leaves the Euro? Do the debts get translated into Drachma or can the government just print Drachma to convert to Euros freely?
If you owe euros you have to pay in euros. If for example the British government owes euros, then they get some funds (perhaps take another loan) and in case this is in a currency different from euros they convert it to euros on the market. If the sum is large enough it is wise not to convert it all at once but in smaller installments. This way the exchange rate stays stable and you can also get a better deal.
So nothing will happen to Greece's debt because they leave the Eurozone. But as the whole issue is political, there could be debt relief/partial bankruptcy because of the same reasons that might cause them to leave the Eurozone.
About printing drachmas:
There is a technical issue to be addressed: It is not the government that prints money but the central bank and their goal is maintaining price stability, not providing the government with revenue. (In time of crisis this may change.)
Printing money causes inflation which in turn will weaken the drachma relative to the euro. Usually when the state prints drachmas all drachmas would be worth less, but states wealth may increase because their share of drachmas increases.
However, this is a special case because there are no drachmas at all. So initially all drachmas would be owned by the state. Hence I think if they print more the worsening exchange rate would balance it out.
What they could do would be to print some drachmas, exchange it with whomever was willing for euros, and then print more. This would only work if printing more is not expected.