Mar 22, 2017 - 01:22 PM
If you go to this site you will learn the your machine can have its memory boosted to 16 GB, although that will still leave you with 512 MB
(about 0.5 GB) of VRAM that is taken from your 8 GB of memory. http://www.everymac.com/systems/apple/mac_mini/specs/mac-mini-core-i5-2.3-mid-2
If you go to this site you will learn all about your machines abilities to handle El Capatan: https://support.apple.com/en-us/HT206886
This site will talk about Sierra/El Capitan. http://www.everymac.com/mac-answers/m... (Add if you look at the side pannel it will give you machine on El Capitan.)
It will also give you some sites in different countries that sell upgrade parts for your mini.
In the USA I have had good luck with http://www.crucial.com/usa/en/?cm_mmc.... For information and parts.
Good Luck and I hope you are successful.
Source: Apple Support, Crucial, and Everymac.com