The .45-70 is a tried-and-true old hunting cartridge. It’s good the seller is throwing in 1,000 rounds of ammo (is it factory ammo, or handloads?).
If you have no other hunting rifle, and you will still have a good .357 revolver and a good lever-action it might be an okay swap.
Me, personally? I’d keep the lever and the .357 revolver and buy a good bolt action .30-06 or .308 or .270.
Good advice