For (1) -- after reinstalling a good and reliable RAM, no need to recompile and just let us know whether some (if not all) of the problems have been solved automatically.
For (2) --- I believe your server is running ISPconfig 2. There is up to the present moment no direct migration from ISPconfig 2 to ISPconfig 3. If you go for ISPConfig 3, then you need to manually reinstall everything (re-create user accounts, reset the password... lots of things to do). If your server supports many clients then you can expect the number of things you need to do, the number of users you need to notify, etc. [For me I cannot afford such a change, but it depends on your own situation]