Nice choice of workout. Can be very freeing to the mind too (well, if not running on say NYC streets).
How beginner are you?
Sounds like not much running up till now?
http://www.c25k.com/ is very popular.
You still have to remember to pace yourself correctly depending on current fitness level.
Stretching is best dynamic after warmup if even needed, usually 5 min walk is good enough, during which some knee bend walking will stretch calves. Afterwards can be more useful stretch time as already warmup up obviously.
https://exrx.net/ExInfo/Stretching
If already fit and just want to run more, many program options here: