1- You could buy a good starter kit. Depending on your project, you might not even need to solder anything, only by using breadboard and jumpers. If not : Soldering station, Soldering iron, Solder, desoldering pump, cleaning sponge, safety glasses, own made carbon air filter ( 
optional) and practice.
2-Again, a good kit will have these kind of sensors.
For exemple, the ARDX come with a Force-Sensitive Resistor, temperature sensor, photoresistor, etc. Moment? I think you mean time. In this case, either use the on-board clock or buy a RTC (real time clock) module (IC= DS1307 for exemple).
3- Distributors — Arduino Official Store
I have no idea if there is a actual shop that might sell them. If they are, I personnally believe that they sell china quality clones. Don't take my words into account, I just trust a little more official re-sellers. If you are aware of any electronic re-seller in your area, this might be your best luck to get anything.