Should I fix my plasma?

I'd hazard a guess that going new might make more sense in the long run.

LCDs and Plasmas are generally not worth being repaired -- unless it was a premium Plasma like the Pioneer Kuro. Given it's a Philips Plasma at 50", you can pickup a Samsung Plasma at 51" for approximately $500 which will give you better blacks and a better picture than your legacy philips plasma. Repairing your Plasma will likely cost you at a minimum $350++ So not worth it.

Agree repairing a plasma is an iffy thing.
First, the person doingthe repair probably NEVER saw another one of your model.
It probably cannot be fixed anyway, and you would still be paying for the repair persons time.
Then even if they fix it, it is seven years old.
As another wrote.. just buy a new TV.

If you have a splattering of dead pixels the only fix would be a replacement panel. If it is even available the cost would probably exceed that of 2 new Panasonic VT50's.
Time for a new TV, 1080p, 3d if you care, digital tuner, lower energy consumpsion, latest technology and all new parts. Fixing a 7 year old TV leaves you with a new part and a bunch of 7 year old parts doomed to fail.
Just my advice.