SNS system team is working more than 10 Joomla migration every week, we will be glad to estimate your existing Joomla site and can provide estimate to you. We guaranty of our services. If we can predict time than we will take on fix cost basis otherwise we will divide project in milestone and will charge as we move on.
Joomla 1.5 is not secured and can be hacked easily, If we do not migrate Joomla 1.5 now than it may be tough to migrate if we do not have migrate path.
Please visit us at www.snssystem.com, submit a request online.