Just bought a 99 F350 with the 7.3

It had a slight hesitation at times and finally threw the po308 code. I took it to my local shop but they were booked, and I was stranded. So, I took it to a different shop and told them what I was told -

"It looks like it has injector cup issues because there is fuel in the coolant. Also looks like it's probably injector #8 due to the year and miles." He also said it's best to replace glow plugs while there and might as well replace all injectors. He said he never replaces only one injector unless it's a new truck with low miles.

They did the following:

valve cover gasket
glow plugs x 8
injector O-rings x8
injector cups x8
coolant
cooling system protector and pump lube
radiator clean
super radiator cooler additive
fuel filter ---- (I had just replaced it days prior to taking it to them in hopes it cleared the code. They said they had to replace it due to the fuel in coolant. $75 for a WIX filter)
diesel fuel supplement
ICP sensor
Exhaust backpressure sensor
oil change
stiction eliminator - HOTSHOT

They then drove it and the code came right back! Never replacing the injector #8. They did a "buz test" and it was fine, so they put it back together with the stiction eliminator and hoped for the best. They said they would give me a deal on the labor but want $400 to install a $300 injector.

1st - Do you agree with what they did?
2nd - Can I drive it?
3rd - If the buzz test is good, should I look at the injector harness before replacing injectors?

I'm broke single mother and this truck is the only thing that gets us up our driveway. Can't afford to be yanked around or damage my truck. I feel like throwing new injector harnesses and injectors on it as the injector rings, G Plugs and all else that's been done.

Homesteading Momma