Interesting analysis here of how a currency changeover might happen:http://blog.variantperception.com/2012/02/16/a-primer-on-the-euro-breakup/
Here's some extracts (taken from John Mauldin's email that referenced the above "primer")
A Primer on the Euro Breakup: Default, Exit and Devaluation as the Optimal Solution
This is an abbreviated version of a longer report which can be accessed at Variant Perception's blog at http://blog.variantperception.com
, or as a PDF document.
Many economists expect catastrophic consequences if any country exits the euro. However, during the past century sixty-nine countries have exited currency areas with little downward economic volatility. The mechanics of currency breakups are complicated but feasible, and historical examples provide a roadmap for exit. .....
The breakup of the euro would be an historic event, but it would not be the first currency breakup ever – Within the past 100 years, there have been sixty-nine currency breakups. Almost all of the exits from a currency union have been associated with low macroeconomic volatility. Previous examples include the Austro-Hungarian Empire in 1919, India and Pakistan 1947, Pakistan and Bangladesh 1971, Czechoslovakia in 1992-93, and USSR in 1992......
The move from an old currency to a new one can be accomplished quickly and efficiently – While every exit from a currency area is unique, exits share a few elements in common. Typically, before old notes and coins can be withdrawn, they are stamped in ink or a physical stamp is placed on them, and old unstamped notes are no longer legal tender. In the meantime, new notes are quickly printed. Capital controls are imposed at borders in order to prevent unstamped notes from leaving the country. Despite capital controls, old notes will inevitably escape the country and be deposited elsewhere as citizens pursue an economic advantage. Once new notes are available, old stamped notes are de-monetized and are no longer legal tender. This entire process has typically been accomplished in a few months.
Breaking up the Euro: Recommendations Based on Historical Precedents
We recommend that any country exiting the euro should take the following steps:
Convene a special session of Parliament on a Saturday, passing a law governing all the particular details of exit: currency stamping, demonetization of old notes, capital controls, redenomination of debts, etc. These new provisions would all take effect over the weekend.
Create a new currency (ideally named after the pre-euro currency) that would become legal tender, and all money, deposits and debts within the borders of the country would be re-denominated into the new currency. This could be done, for example, at a 1:1 basis, eg 1 euro = 1 new drachma. All debts or deposits held by locals outside of the borders would not be subject to the law.....
Impose capital controls immediately over the weekend. Electronic transfers of old euros in the country would be prevented from being transferred to euro accounts outside the country. Capital controls would prevent old euros that are not stamped as new drachmas, pesetas, escudos or liras from leaving the country and being deposited elsewhere.
Declare a public bank holiday of a day or two to allow banks to stamp all their notes, prevent withdrawals of euros from banks and allow banks to make any necessary changes to their electronic payment systems.
Institute an immediate massive operation to stamp with ink or affix physical stamps to existing euro notes. Currency offices specifically tasked with this job would need to be set up around the exiting country.
Print new notes as quickly as possible in order to exchange them for old notes. Once enough new notes have been printed and exchanged, the old stamped notes would cease to be legal tender and would be de-monetized.
Allow the new currency to trade freely on foreign exchange markets and would float. This would contribute to the devaluation and regaining of lost competitiveness. This might lead towards a large devaluation, but the devaluation itself would be helpful to provide a strong stimulus to the economy by making it competitive.
Expedited bankruptcy proceedings should be instituted and greater resources should be given to bankruptcy courts to deal with a spike in bankruptcies that would inevitably follow any currency exit.....
Institute labor market reforms in order to make them more flexible and de-link wages from inflation and tie them to productivity. Inflation will be an inevitable consequence of devaluation. In order to avoid sustained higher rates of inflation, the country should accompany the devaluation with long term, structural reforms...
We will later explore which countries are best placed to exit and which ones should stay. Greece and Portugal should definitely exit the euro. Ireland, Spain and Italy should strongly consider it.