You don't need a pivot pin install tool.
Look closely at the buffer spring retainer pin. You'll notice it fits quite nicely in the pivot pin hole. That's your install tool.
Insert spring, then the detent. Use the buffer spring retainer pin to "capture" the pivot detent. Now slide in your pivot pin, using it to push the buffer spring retainer pin out the other side.
I do recommend safety goggles, just in case, of course.
A small hammer with both nylon and brass heads is helpful. Brownells sells a nice one.
I believe I used a spare firing pin as a roll pin punch, but I don't really recommend doing so.
The tip about electrical tape is a good one. Especially if you're working on someone else's lower.
The Stag stripped lower I assembled with a CMT parts kit has the nicest trigger I've felt with an AR-15, and it's single stage. Your results may vary.
Good luck with your adventure, and welcome to Black Rifle Disease!