There will be no reason for you to have concern over the surface rust on the driveshaft. GM hasn't coated shafts for MANY years. Rust-through isn't an issue
If it was, you'd see problems all over the road.
You should find a better friend to have automotive discussions with. Driveshaft failures do not result in explosive damages sending shrapnel around. Rarely (except in cases of high HP machines) does the actual shaft TUBE fail, instead the failure is at the yoke. When the front yoke fails, you do have the POTENTIAL for the shaft to drop down, impale the road and lift the vehicle. Safety loops are required on drag racers for that reason. Rear yoke failure simply drops the shaft harmelssly at the back, and leaves one with no motivational forces to move.
Resist the temptation to get under there with a wire brush and can of spray paint. Rarely will you achieve a proper even coat, and instead you'll create an imbalance on the shaft, thus leading to a vibration at some speeds while driving, thus more frustration, thus a reason to ask your friend about it, thus his explanation that your muffler dampening fluid has reached a combustible state and will soon cause an explosion in the blinker fluid dispenser.
K&N won't cause HARD shifting. As mentioned, it has been questioned by GM in regards to confusing shift signals by oiling the MAF wires. If you haven't maintainted the K&N yourself yet, this isn't an issue. It becomes an issue when people attempt to maintain the K&N filter and have no clue how to do so. "If a little oil is good, a LOT must be much better!" - doesn't work! People also tend to over-maintain the filter. A layer of dust is DESIRED on there, not to be immediately removed. The dust creates increased filter surface area. Proper cleaning should be infrequent, and when done the re-oiling should be very minimal and be let to dry to the element before use.
