I shoot two Pietta 1858s and I have never experienced a lever problem. I will have to agree that maybe on You Tube you are watching someone fire a Walker.
When you get your piece, come back with what you have and what you need. There are so many different sites that it would be hard to direct you. A couple of sites for parts and equipment are:
http://www.dixiegunworks.com
http://www.kitterytradingpost.com
But we need a little info in order to better direct you. But the Remmy is a good first choice. Though I own and shoot the 1858, my heart lies with the 1851 Colt Navy or the 1862 Colt Navy. I just like the feel of a Colt. But the Remington is easier to swap out cylinders and with my son, it is his favorite.
Welcome to the world of smoke and balls.