This unit happens to be one of my specialties and we work on them most every day in my shop. I used to work for the recording studio branch of URC back in the late 70's.
You have a valuable unit there and a lot of people would be glad to buy it from you, me included.
The F series is more desirable and valuable than the G series and you should keep it as original as possible.
It uses 2 FET's. Q1 is for audio gain reduction and it can be replaced with a J110 FET. Q11 is for meter gain reduction and can be replaced with a J202 FET.
The 1N2989A is available, though a little hard to find. There's often heat damage where it connects to the PCB so be sure to clean everything up nicely. The lamps are "before" the zener and power resistor in the power supply, so a lamp fault would not damage the those parts, but they do fail sometimes.
Be sure to replace the power supply caps too.
Check out my web site for lots of info about UREI and the URC companies. BTW we have all the 1176LN parts in stock and I'll give you the ARF good guy discount if you email me.