99 suburban - bad rod bearing(s)

I know this wouldn't be the best way to do things, but how hard would it be to replace the rod bearings in my 5.7 without pulling the engine?

You cannot do this. The engine must come out to remove the pan.
In the good old days of the straight axle Suburban 4x4, you could pull the pan with the engine still in the car, but not with an independent front suspension chassis.