Road noise is not really typical in the 01 is300, but my car has been turbo for a long time and I cant hear anything over the sweet sound of it spooling.
All in all, the 01 IS is an excellent car. Run mobil 1 oil in it, keep with the factory equip, air filters, etc, unless it isn't a daily driver. Mobil 1 is worth the money and you should run this oil in your car. It cost more, but is worth every penny.
When I had my engine rebuilt at 130K, the report was that the engine parts looked like new, except for the cracked piston lands (from running too much boost and 50 shot nitrous at the same time for years on a stock block).
Brake fluid... whatever dot spec is on the lid of the brake reservoir should be fine. Nothing too special there.
The clicking sound is odd... I never experienced that.
I would recommend making sure that the timing belt was replaced at 60k. If it wasn't, spend the extra bucks and have that done.
The stock cd player is junk. Throw it away. However, the factory wiring has an amplifier built in that will have to either be bypassed, or you will need to run new wires to the speakers.
You can get by with the stock speakers for a while. Just have someone that knows what they are doing install the system.
When I bought mine, I pulled the interior and dynamatted the whole car inside, so it gave me the chance to rewire the whole sound system.
If you know what you are doing, you can replace the head unit and rewire it all in a few hours.
You can find a wiring harness and a single din mount kit for a cd player on ebay for cheap. try an alpine cd player... They have a nice orange glow to them that is close to the stock amber.
The bumpy gear transitions sounds odd to me. When I first bought mine, it was silky smooth. The turbo kit forced me to change to a fully built race tranny after the factory one died. The race tranny shifted so hard that it felt like someone rear-ended me everytime it switched gears. Most of the time, second and even third would chirp the tires.
For your car, it shouldn't be like this. Unless someone has modded the car or increased the line pressure in the transmission, I would have it checked out.
Rebuilds of these transmissions are expensive.
All in all, it should be a good car, if the rebuild was done properly and it has been maintained. The biggest problem that I know of with these cars from stock is aroung 170-190k the valve stem seals in the head will start to seep and the car will burn oil and smoke. It doesn't happen in all of them though.