Please feel free to contact me to discuss further at your convenience.
I've done this exact same requirement many times within my current full-time employment position as Head of IT, as well as many times in the past. Though I may be new to Freelancer, make no mistake, I'm not new to professional project management, meeting client needs, completing projects on time and within budget AND owning the project through to completion at no additional costs.
Of course, in addition to the completion of the work required, you will receive full documentation of the completed program. All other bidders should be offering you the same so that any future work on the program does not require you to pay for someone to 'learn it'.
Once I see the information we'll be working with, I may have additional questions regarding 'a way to deduplicate data' to ensure you have the expected outcome desired, but beyond that, I look forward to working with you.
Thanks for your time.
David