Sirius radio???

I have a 2012 Dodge 1500 regular cab long bed.
It is equipped with Sirius radio from the factory. I haven't been able to get it to do a damn thing.
I never registered with anyone and getting notices daily from Sirius themselves (have no idea how they got my info since "I" never gave it to anyone related to Sirius.) Supposedly I had a "3 month free trial" but could never get it to make a peep.

Anyway my son and daughter in law have a plan and it was much cheaper to "shirt tail" on their plan.
Never had Sirius before, but have used it when I have been in others' vehicles.
The stock radio works fine, speakers sounds "good enough" for me as I'm no aficionado or loudness competitor. But I push "SAT" and I get one of 2 messages in the display, usually it is "updating channels" endlessly until I go back to AM/FM.
I love the idea as I'm always channel surfing as I lose range on one station to the next area, and I'm so tired of "talk radio" all the way to work and sometimes for the ride home as well.
So far I have swapped out the radio with an identical but "known good" stock replacement, programmed to the son's Sirius account. I bought a new cable from Dodge, I didn't realize it was 2 sections. They only sold me 1 section. The parts counterman assumed it was 1 pc all the way to the antenna. Nope. It was long enough with the headliner down to reach from the radio to the antenna, I did pull the wire out of the plug on the cable end of the original cable where it plugged into the antenna, I need another section to reach from the kick panel to the antenna because of that. But with that new cable plugged into the antenna and the radio still "no dice".
I want to replace the antenna, mine is the flat one, no " wing" like some I see.
Mine is mounted towards the back passenger side of the roof. Newer versions of my truck have it closer to the front edge.
Are these antennas universal sized? Or do I have to go back to the stealership and get that exact antenna to fill the hole?
Is there another source?
Where can I buy these cables? (BESIDES THE DEALER)
I see they seem to be color coated, I don't know how interchangeable they may be. I'd rather have 1 continuous cable that will reach the antenna directly rather than a 2 piece cable, the more connections means more chance of corrosion and connection issues. Like sgt Schultz on Hogan's heroes TV show "I know nothing" about satellite radio. HELP!!!!!