Owing to the Wifes machine suddenly developing an intermittant issue and the daughters monitor dying, i thought I had better get organised

Question One

So i have ended up with a couple of machines (I have yet to fire them up) both have 4 GB of RAM DDR3 (the small laptop looking one so-dimm? )

HP Elitedesk 800 G1 usdt (1 x 4Gb)

HP Elite 8300 usdt (2 x 2gb)

The specs say 

Now when i checked the Elitedesk 800 machine it contained a 4 GB stick that said PC3L, and when i looked that up it said that, that is DDR3L or low voltage RAM which is backwards compatible with DDR3, correct?

So i should be fine buying some sticks of that DDR3L ram, as it does appear to be cheaper on trademe at about $40 for two 4gb sticks

Question Two

Is it worth buying a second hand monitor, or is it best to go new, I have the Warehouse and Noel Leemings as the nearest bricks and mortar, where I can actually view monitors, but to be honest I am finding it hard to justify buying new