Anyone know how these engines handle cam swaps and those kind of upgrades? i aint to farmiliar with the fuel systems on those engines  

A 5.9 Magnum engine is simply an upgraded 360. As long as you get the cam and other related parts you're thinking of changing to fit a Magnum engine, you should be fine.  

I was told that thost engines are a pain to tune after a swap like that  

IF it's an EFI engine, you might have to get a special tune done to it by someone that has EFI tuning capabilities.  

Your right about the tune, also the Magnums with their Chevy style rockers don't like cams with more than .500 lift, they tend to push the rockers off to the side, this is were the LA headed motors are superior with their fixed shaft mounted rockers.  

Im just going to run a mild cam to help with turning the bigger tires  

Dr, you can use more than .500-inch lift cams, you just have to change the rocker studs for larger ones.