I'm buying a R510 with no CPU or memory. Need some guidance

I'm re-building my freenas system and want to use a R510 12 bay enclosure.  I'm buying a barebones R510 with No memory or cpu but comes with heat sinks.

I have a pair of L5630 Xeon CPU's that I'd like to use.  They came out of a R710 that I upgraded.  I'll also need to get memory.  Here are my questions.

1. Will the L5630 CPU's work in the R510 (I googled and saw that others were using them)

2. What if I only want to use a single L5630 CPU to keep power consumption down.  Server will be used to hold Backups so overall power of machine is not terrible critical

3. Will want 16 GB of memory, if only using 1 CPU, what memory configuration should I use? 4x4GB ECC DDR3? 

Thanks,

Roveer

      3a.  With L5630 specs say DDR3 800/1066 is what is supported by CPU.  What memory should I use? 

      3b.  Does it make any difference if I decide to use 2 CPU's? 

      3c.  What slots should get populated?