Tachometer Issue

[teflon44]

Hey all,
I am new to the Toyota forum and somewhat new as a Supra owner. I have an issue with my Tach (the in-dash stock tach). It is completely non functional. The person that sold me the car says that there is a component in the rear of the tach that needs replacement, but I can not give much thought to his suggestions as I have had to do some significant repairs to his shoddy work on electrical stuff.
My question is that I hear there are often issues when a SE is modded to a TT (as was the case with this car) and that the tach and AC are normally not fuctional (yes My AC/fan/heat doesn't do anything either). Is this normally the case? And what are the normal causes remedies?

Any help from the experts is appreciated!!!