So, changed the fluid. The oil that came out looked brand new. Topped it up with two quarts of redline 75-90 and the car feels EXACTLY the same. I didn't expect any difference in the way it drives but I am glad I got that job out of the way.
Btw, incase anyone doesn't know already. Gear oil is the worst smelling fluid you use in your car. I suggest you take your time removing the drain plug so it doesn't coat you in the stench.