Hello,
I can finish it in few hours. For me it will just the total time it takes to download and upload it to your new domain. About the subdomain issue, it's a work of few minutes for me. I have experience and knowledge of doing this as we have more than 100 customers of open cart. And we manage their open cart stores. You can pay me after I complete your work and you are satisfied with it. If you want to discuss or clarify anything, please feel free to contact us via chat or message here on freelancer.com
Regards,
Prashant Gautam