Hi Scott,
What exactly is your objective?
Do you want to design your own RF PCB?
Do you want to buy existing modules and put them into a weather proof box?
I designed some pcb's using Kicad and JCBPCB to make and stuff the pcb. I found it is cheaper to buy existing modules.
If you are interested in 21 cm Hydrogen Line a good place to start is with SARA's Scope in Box or The Discovery Dish with Discovery LNA.
A good rule to follow is place the Now Noise Amplifier as close as possible to your antenna feed and all digital electronics as far away as possible from your antenna.
It is difficult to answer your questions without knowing more specifics.
Stephen