I use to run one of these servers for a local University and never had any issues with it for the 4 years I was using it. If there was anything that came along that was not right it would throw out a warning that created a log entry. Find the log and read what it has done. Also I had it set up to notify me by email of any issues and it would send out one if it was not happy about something. Go to the site Markus Weiher mentions above to set up these functions. Also Make sure you have a large enough power/battery backup on the unit.
It is good you bought the server with the service package with it so you have the spare parts. Did it come with spare fan also? Check to see if all the fans are running. This thing is very loud. If yours is not then the fans could be the issue. Make sure that if you try the replacement board you have someone who is use to working with a static mat so they do not zap the board. Do Not Take It Out Of The Bad With Out Using Grounded Static Strap!!!
Good luck. But learn the Management system for the server before starting to tear it apart to fix what may just be a setting.