Reading multiple manuals is a waste of time. Info's all the same. YouTube is not the place to learn about anything either.
Yes, any currently available press will do nicely. You will need a bunch of other kit too though. Have a look at one of the beginner's kits. They give you everything less dies and shell holder. They come with a manual, but buy a Lyman too. The Lyman is just more versatile than any powder or bullet makers book.
RCBS' warrantee covers the kit forever, not who bought it originally. So your dies are covered. If you have any issues, even if you caused it, RCBS will fix it with a phone call or E-mail. No questions asked other than your mailing address.
Reloading equipment can be bought Stateside and shipped or brought across the border with no fuss. Reloading components cannot.
The .45-70 comes in a few different rifle types. 'Types' being about the strength of the action. Only matters because some of 'em are suitable for reduced black powder equivalent loads only. Like the TrapDoor Springfield. Your rifle is considered to be a modern rifle(despite its heritage) so you can use those loads from the Hodgdon site. The cartridge can be loaded up to near .458 Win velocities or nicer on the shoulder mid range loads.
Oh and read the book.