Question about updating to macOS High Sierra

4GB RAM is a bare minimum. Although Apple specs state 2GB minimum, this is unrealistic for smooth performance. I'd suggest 6 to 8GB as a minimum.

If you want to test High Sierra on your Mac, install it on an external disk and see how it performs.

I had the same model/specs (but the 2012 model) and I upgraded it to every new operating system as they were released. I traded it before High Sierra but did use it for awhile with Sierra. I saw no negative performance impact and I doubt that you would with High Sierra either. If I still had mine I would update it but you may want to wait to see if you get more input from someone who has done it.

Yes, the SSD should help significantly. It will be converted to APFS file system from Mac OS Extended. If your external drive is rotational then that will not be converted to APFS.

Well FoxFifth had the same model and there's no more impact on RAM from High Sierra then from Sierra, so it might be OK. As I said, test on an external drive first.

macjack wrote:

... there's no more impact on RAM from High Sierra then from Sierra, ...

That's my assumption too -- but no personal experience.

It would also be doing the same thing with your current Yosemite OS.