How easy is it to upgrade the RAM in an Optiplex 3070 SFF to 16GB?

Yes, it’s an easy upgrade. The 3070 SFF supports up to 32GB of DDR4 2666MHz non-ECC desktop RAM. Opening the case takes two thumbscrews, and the RAM slots are unobstructed. Just push out the old sticks and push in new ones until the clips click. Any decent DDR4 2666 or 2400 will work, and no BIOS updates are needed.