Upgraded ram from 1 GB to 2 GB.
Taking out the case was the biggest challenge. I initially tried couple of tools, but they almost damaged the edges of the case. The machine is very old and case was not easy to pull. I saw a video demo of iSesamo tool on youtube and ordered from ifixit. The order was delivered on time in India and initially I had a doubt if the tool will really work because it looked too soft. But I was really surprised the way it worked. Initially I had some difficulty as the case was too tight but I am quite sure if I had used some other tool, then my case would have been damaged. With the help of other tools and video/guides, other tasks were made easy. Apple authorized shop asked me around $150 for this upgrade, but I managed to do it myself @ $30. My order at ifixit cost me around $90 but I can use them for future repairs. So over all I am in profit. Thanks ifixit.
If you are trying to open old mac mini (not unibody), then better order two isesamo tool as it can help pulling the case. You can pull one side and block it with one tool, and they try pulling other to open the case.
Metal Spudger Set
Anti-Static Wrist Strap
iSesamo Opening Tool