Hello,
I have done many Quickbooks integration projects. You can refer my past experience. Due to some personal reasons I had to take break from work but I am back now and would love to work on this project.
I assume you both the applications are on same system and you need to move data from your software to Quickbooks.
The challenge with this is that your software should be able to provide some kind of mechanism to export the data (in any readable format like XML, CSV, Excel, etc). Or else it should provide database access to read the data. The database access would make the task difficult for anyone since as a developer we would need to understand the architecture of the software.
Once we have the data in readable format we can then convert into compatible XML which can be easily used by Quickbooks SDK.
My cost is little bit on higher side since you have not mentioned what all data (Invoices, inventory, Sales orders, customer, purchase orders, ect) needs to be moved and I assume its all of them.
Thanks,
Kavita