So, in case if my Lenovo ThinkPad T500 laptop has only two memory slots, then, I will have to buy 2 pieces of ThinkPad 4GB PC3-8500 DDR3 Low-Halogen SO-DIMM, and replace my existing 2 X 2GB modules in order to get the 8 GB?
* How easy is it to install/remove RAM in Lenovo ThinkPad T500 ???
Is there a diagram or video online that can show me how?
The T500 only has two RAM slots, so upgrading to 8GB would mean that your existing two 2GB modules would need to be removed. You could keep the 2 X 2GB modules if you wanted to return to a 4GB config in the future, used in other systems, or potentially sold online.
Replacing the RAM is simple; remove the four screws for the palmrest and the memory slots will be right under the palmrest. Refer to the HMM for more detailed instructions: http://www-307.ibm.com/pc/support/site.wss/MIGR-70068.html. Video proceedures for installing memory are available on the Lenovo website. Since the T61 ThinkPad is mechanically similar to T400 / T500, you follow the instructions for it's video.
You'll want to make sure all power sources are unplugged from the laptop, and that you are grounded. Try to avoid touching the pins in general.
NOTE: You can use most 4GB DDR3 modules, that are specified as 1066 MHz, although you won't realize any benefit from installing memory that's faster than DDR3-1066, because 1333 memory just downclocks to 1066 in the T500)