CF-19 MK4 (4gb RAM to 8gb RAM)

I am looking to add 4gb of Ram to my CF-19 (CF-19RHRAG2M) Which currently has 4gb of RAM, for a total of 8gb of RAM.

What is the best option in regards to reliability and cost. Perhaps something on eBay, has anyone had good results from purchasing RAM from eBay?

Installation: I am assuming the additional RAM is plug and play, are there any other steps required to installation other than sticking in the new RAM?

Thanks