I have a double-basin kitchen sink, and the drain line from the garbage disposal is completely clogged. I've been unable to clear it with drain opener, so I'm looking at replacing the P-trap, but space is a bit tight. The pipe nut just on the drain side of the P-trap won't come loose - I've tried WD-40 and several different wrenches. Given the pictures that follow, how much of the drain system should I try to replace? Or should I simply call a professional, given the tight spacing between couplings?
The non-disposal side of the sink is not clogged, and is draining normally. I'd prefer to not replace that part of the drain system if I don't have to, but I'm willing to if I can do the replacement myself and need to replace the whole system to do it sanely.
EDIT: I'm pretty sure I'm turning it the right direction - it won't budge in either direction, though. I decided to punt and cut the downpipe coming from the disposal leading to the P-trap (intending to snake the trap and replace the downpipe with an extended with two slip joints) - and yes there is a slip joint from the disposal to the downpipe - and the clog is in the disposal itself. The pipes are completely clear. Since the disposal has been giving me problems (the motor won't turn the blades when I turn power on) for about 4 months, it's time to just replace the disposal. I'm not comfortable doing that myself, so it's time to spend some money on a professional. Thanks for all the help.
Image 1: the P-trap below the disposal:
Image 2: the joint for both "halves" of the sink drain: The longer pipe coming "down" comes from the P-trap below the non-disposal side of the sink.
Image 3: P-trap below non-disposal side of the sink:
Image 4: the non-disposal side where the dishwasher waste line comes in: