There is a lot of free software out there that will monitor your cpu and gpu fan speeds and temperatures. I had a couple of them installed and uninstalled them. For the life of me, I can't remember their names. Hopefully, one of the other guys will recommend one. If the fans are really dirty, you should clean them.
When you install RAM, it has to be installed in the correct slot (s). You would need to look at the motherboard manual to see what that is. However, if you put the new RAM in the same slot (s) where the old was, you shouldn't have to worry. You should definitely reinstall the RAM (obviously, it's not going to do any good if it's not installed). Note that when you install new RAM and you install more than one stick, the specifications of each stick should be identical to the other.