I have been working with DNN since 2003 and have setup many sites, developed skins, modules, etc...
The RFP is kind of vague, what exactly are your requirements?
If the project is to simply copy the site & make a few skin changes then the cost will be reduced significantly.
For proper testing I have proposed a 14 day window.
Please note; DNN is written in Visual Basic, and C#, there is no PHP code what so ever in DNN.
Regards,
John H. Ward, Jr.