Yep, it's necessary. Best advice I can give, is if you start getting frustrated, walk away for a bit. Been there, done that myself.
I highly recommend the slave pin. If you don't want to do polishing, that's ok. It'll just take a bit to work in. (Polishing is well worth it IMHO)
You can replace the lifter without taking the whole sear apart. Once you have the sear out (with the slave pin holding it together) just gently push the pin over until the lifter and spring come out. Then replace and slide the pin back.
Careful of that little lifter spring, they can shoot into orbit. Make sure to order a couple spares