Your system will automatically detect new RAM on each boot so this will not affect your current image. Basically it will do this for all new hardware and will have no problem unless new drivers need to be installed that are not part of Windows already - with RAM it has no problem - assuming that the new RAM is compatible and does not exceed the limit that the system might have.
This is a link to Macrium imaging - Imaging with free Macrium
Note the remarks about USB 3.0 devices. I don't have any experience with these yet.
I have used Macrium Refect Free 4.2 with the Linux boot disk and have had no problems restoring images but all my images are on internal disks. If you can go through the whole restore process and locate the required image then it should restore OK. There is usually an option to back out before committing to a restore as the last step.
Hope this has been of some help.