Do a search for sure to find out who has claim to the ground first. Wherever the records are stored, start there, and I imagine there are software programs that will help you out as well.
Your detector will find lead just like it'll find gold, but I wouldn't want you collecting lead any other way.
Good luck detecting your mine dumps as sometimes there are chunks of ore that got tossed aside, especially with hand sorting. Your detector will be able to sniff out the good stuff.