It should not be a problem at all.If you have paid nothing since registration, you will have to go to ETO office to get the copy signed and stamped by them to extend your deadline of payment of taxes.There should already be a stamp but that is normally valid for a month or so and there is also mentioned that from which date you will have to pay the applicable taxes.Then go to the post office and register there for token tax payment.Normally they now say to go to the post office in the same area of which you have written the address in your registration book but anything is possible in this country so register it in Post Office that suits you.Let me know if any help required.
You will pay the Withholding tax for each year @Rs.1750 for 1298CC car.There is no penalty/late payment surcharge on Withholding Tax.
And as for as Token Tax is concerned you will pay Rs.384 instead of Rs.348 for each year.There is no penalty in Islamabad for late payment on Token Tax as per my experience.
In NWFP they charge a huge amount as penalty on Token Tax(Token Tax rate already very high e.g. for 1298cc car @1800 per year and almost the same amount as penalty on late payment if late payment is done after a year).
And there is no penalty on late payment of Withholding tax in any district of Pakistan.