When running a Mac mini server, many people see quickly that the more RAM the better. To have Apple install the RAM can be quite expensive, but you’ll know it was done right and is covered in the future.
However, if you want to try it yourself, it is much cheaper and not too difficult.
The new Mac minis make it very easy to install RAM. Just turn the black circle on the bottom, and you’ll see the RAM slots. You can add up to 16GB of RAM.