Drum traps belong with button shoes and buggy whips. Yes, it can be replaced with a P trap. Your connections should be made with no hub, aka banded, couplings. They are similar to the neoprene sleeve as pictured, but they have a stainless steel band around the whole sleeve. Neoprene couplers like you have are not supposed to be used above ground as they don't provide enough support to the joint, and while they obviously work, the no hub is better. As far a removing the lead, I'll leave that to the pros. If it was mine, I'd replace it, but that's just me. Besides the dangers of lead, I'd be concerned that the lead might deform when clamping the no hub. Don't that this last part as the final or best answer.