Drivetrain Issues, help please!

[AxiOn419]

Finally took the car for a drive on the open road today. There are a couple issues I am concerned with.

Car: s13 hicas w/ rb20

1. When I start driving in first gear, as soon as the clutch engages and the car starts to move I hear a very loud high pitch squeel noise. It does not last long and has been doing this for quite some time (when the engine/transmission was in my old s13). Input shaft bearing maybe? If so, is it difficult to replace?

2. I am getting a little bit of noise from the gearbox area. I just saw tonight that I was dripping some gear oil from the input shaft area. So I could possibly be low on gear oil. How much of the input shaft should be sticking out of the transmission? There is probably a good 1.5 to 2 inches of silver input shaft showing. Is this too much? Would that cause a leak? I am going to investigate further tomorrow. Could the leaking possibly be a blown input shaft seal?

3. Not sure if this is my drive shaft, but in low speeds it is more noticeable and is present at high speed as well. I hear a thunking type sound. It is coming from the mid section or rear of the car. It feels like something is hitting the bottom of the car almost. I am thinking it is either a driveshaft issue or the exhaust hitting up against something. I have looked and do not see anything that it could be. Is there any way to test and see if my driveshaft is balanced and rotating properly?

Sorry for all the questions but I am in need of assistance

Thanks