Hi jay_b,
if you've used postman before, then stick with it for testing of the relevant calls and parameters they use.
with regards to powershell, i wrote the one posted in the link below and just used google and postman to help me.
postman for how the calls etc are formatted and what json results are returned and then google on how to create functions and subroutines,parse json data, use arrays etc in powershell.
rgds
Gary (nealgs)