Fan working or psu getting warm are not sure signs of working psu.  A failing or failed psu can do both. Your dilemma is you do not know whether it is motherboard or psu having issue.  To prove motherboard is bad, you need a good working psu that fails to make pc post.  On the other hand if a good psu revives 960, then the OEM psu is bad.  If you do not have access to a good psu, it may not be worth having someone repair the system for you, as repair shop cost likely exceeds getting a working complete system that is newer.
Hello this morning when I turned on my dell optiplex it had a error code of 34, I searched online that I had to remove memory slots and reads them so I did. after I did the computer still shows up with 34 code but no beeps no display too.  
Dell Optiplex 960 yellow 34 code