Hello there,
First of all, I'm sorry to start like this, I have to say I just put 2500 USD since your requirement is not fully understood with your bidding margins. But this may help to initiate the discussion.
1. Styling, If you have not already developed any theme, then we have to develop a theme, based on your experience with current Open edX instance, I think you may agree on that. To develop the Open edX theme, we need to put some effort and time.
2. Configurations, If you just want to know LMS & CMS configurations working correctly or not, that thing I can do it for free. But if things are not correctly configured or installed, then we may have to redo the thing.
3. Ecommerce, For that you can just try to make the payment by your self with a sandbox account and can figure out things are working or not. Or I might be able to help to test for free.
So my question to you is, if things are not working, do you want us to develop/fix/reconfigure your instance for above your bidding limit?
Thank you!
PS, message me if you want to clarify any Open edX queries.