[Yaesu] Pin diode mod. FT-1000 Ron

[Ron Burns]

I am a new owner (3-months) of a ten year old FT-1000. I think the fan
failed and I cooked the finals. So, it's about ready to go to the Yaesu
hospital.  I've heard the" front end pin diode" mod mentioned  frequently.
Could someone explain what this mod is and what it does and how could I tell
if this mod has already been accomplished?  Also as long as it's making the
trip are there any other updates I should have included? Thanks for any
help.
 .