Here's the outline of your server's specifications.
You need the CPU fan and heatsink in order to boot.
You need a chassis fan to boot.
The RAM requirements are outlined here. PC2700 DDR SDRAM @ 333MHz
You can use another controller, but it's best to stick with the server's intended storage controller. ML350 G4 systems use U320 SCSI disks, so the best RAID controllers for the model are the HP Smart Array 641 and 6400-series controllers.
Edit:
You obtained this server from some source. I would go back to that source to obtain the necessary components. It's not worth spending much money to acquire them, though. This is a very old server and may not be a good investment.