1. Basically, yes. But you must get the right model.
2. See no. 3
3. There are 2 types of RAM slots, DDR & DDR2. DDR2 is the newer one. Make sure you understand the type you have now. Download a software called PC Wizard, it will help.
4. I suggest Kingston, Samsung is alright.
5. You will need to know the maximum supported RAM size of your mainboard, too much RAM may cause damage.