A 1X scope is a big improvement over iron sights, I must admit that IF you live in a state where you can use more power I would get at least a 1.5X4.5 but that's not always the case and if you must use bifocals or trifocals a 1X can be necessary for accuracy. As far as I know the lifetime warranty is on guns,I can not recall ever hearing of a lifetime warranty on scopes.
Used scopes are very chancey the brand does not make any difference; all it takes to ruin a scope is dropping it so the gun is on top a slight bend in the body will cause parallax and accuracy is no longer possible I have ruined several that way[as much as I hate to admit it]. I do not buy used scopes.