There are onboard LEDs and front panel LEDs. Some chassis even have back panel LEDs. You need to make it clear.
Certain boards are stock boards, but certain boards are made slightly differently for the type of chassis the board is in. I have the S3420GPLX board and the front panel connectors are different from the technical manual. All the jumpers and other settings should be printed on the chassis side panel. But you do not have it.
In order to boot, you need a good board, power supply, CPUs and RAMs. That is a large board and I do not think the 4 GB RAM was the original configuration. Check the RAM specification and make sure the DIMMs are supported. Most of the XEONs require RDIMMs. And certain RAM slots should be filled first.
With all the above, you'll need to figure out the power switch button. This is very important since you do not want to connect the wrong pins....