I don't understand 'leans to the front'?
I would watch all the components in the front end while somebody else turns the wheel, to determine what is loose/worn.
Balljoints are generally replaced in pairs, upper and lower in each side. Not required, but you've already got it apart and why do it twice? It requires pulling the bearing assembly and axleshaft, and removing the steering knuckle. Most auto parts stores rent the balljoint service tool.