I am building a diorama of an 1/35 RQ-7B launch site and need some advice during production as the layout is the largest scale I have done. The biggest problem for me has been my previous projects were show room condition cars. Now I have a lot of weathering, detailing, and fabrication I have not done before. All advice and ideas are welcome.

Your question is pretty open-ended and entire books have been written on the subject.

Here's some information to get you going:

AMPS 2013 International Convention::Bases and Groundwork Seminar Slides

I'd suggest that you dial in your request for information into more discrete bites and ask about things in a more specific way.

There's no shortage of advice here on how to do just about anything.

Good luck!