You need a more compelling argument than your own convenience. This argument should be on your Xanga page alongside the link to the website your assignment is on.
E.g., if you were working for a company and they hired you to update and improve their web pages and have you the existing stuff and said "modify this". If you then replaced everything, they would be annoyed, unless you could convince them that there were reasons why this would be better.
Given the time remaining, I am happy for you to either exchange e-mails with me to negotiate, or to put a compelling argument as to why your assigment needed to be off xanga because of some reasons which are not convenience. E.g. you wanted to do something xanga would not allow (but indicate you tried it on xanga) or that something else you were doing needed a different site etc.
In essence you don't get something for nothing! If you get the increased convenience of not being on xanga, the cost it you need to justify it, which is probably as much work as saved by the increased convenience. (And this would be the same in the real world as indicated in my e.g. above.)
If the web page is for a club or other organisation, this is easy.