Audio stuck on "Digital Out" - headphone jack problem?

Hi

I have a Mid-2009 Unibody 15" MacBook Pro, which has been a solid workhorse for over four years.

I noticed a couple of days ago that I can't get any sound coming out of the internal speakers. I think it is a hardware fault with the audio-out jack, incorrectly reporting that an optical cable is plugged in. Basically:

• Headphones sound fine. When a pair of headphones is plugged-in to the audio-out jack, the device for sound output in the "Sound" Sys Prefs says "Headphones". No problems here.
• Optical-out works fine. When an optical cable is plugged into the audio-out jack, the device for sound output in the "Sound" Sys Prefs says "Optical Digital Out Port". No problems here either.
• When NOTHING is plugged into the audio-out jack, the device for sound output in the "Sound" Sys Prefs still says "Optical Digital Out Port". There's also the red light shining out of the jack, and no sound coming through the internal speakers.

There's no bits of broken jack plug suck in the hole. I have tried SMC and PRAM reset. I presume that the audio-out jack is just worn-out and thinks there is an optical cable stuck in all the time, except when there's some normal headphones in there. I presume the audio-out jack needs to be replaced. I presume this is solidered directly to the logic board, and is basically impossible.

Anyone any more positive ideas? They'd be greatly appreciated.

Regards

SL