pleasew8,
Something FREE that will be of good information for you to learn some of these things is to go to this Ford website,
https://myford.fordvehicles.com/serv...e&ord=29819523 and register your VIN. Then you can download in PDF form the Owner's Guide (different from the owner's manual) for your Mustang and probably find a lot of answers to questions you'll be having.
As for key fobs, try eBay. I recently picked up a
new one for my son-in-law's 2000
Stang for $3.99 - $10 after shipping. Of course, that was the rare occasion. Over the years, I've mostly paid between $20 and $40 for new or used ones for different cars on eBay.
Good luck.