rough country makes nice stuff for yj's. regearing is not a must, but a good idea. i've wheeled the crap out of 4 bangers w/ spring over lifts and 33's and never broke. it depends who's behind the wheel, but the 4 banger is kinda nice to wheel cuz it doesn't have the power to really hurt itself unless you try.
i would not lock the stock axles personally.
i would suggest if you're new to jeeps, do a ton of research on what lift you think you want, to help reduce the
factor that i've seen a million times. also search soa lifts, and decide what you wanna do with your jeep. i'd do the lift, and tires, and then see how you like it, and where you wanna go next. before you spend thousands on lockers and gears for stock axles. just my input