401k Plan

Hi,

Was looking for information on 401k plan.
Canadian citizen living in US on GC and relocating back to Canada:
(1) Can I leave my 401k plan as is to avoid the early withdrawal penalties?
(2) If leave in current plan until retirement age, can I withdraw from this while living in Canada, no longer being a US resident?
(3) If leave in current plan until retirement age, how are the taxes calculated when withdraw from this account at retirement - do you pay Canadian tax? US tax? Both?
(4) If leave in current plan until retirement age, do I need to file US tax returns forever?

Thanks in advance!

IRAs are treated as RRSPs under the new 2008 tax treaty, there isn't much info on the web about it but essentially the rules now are identical as for an RRSP once you move back to Canada, you'd have to talk to the CRA directly about the specifics as the treaty is new.