The hash rate is easily obtained from 'getmininginfo' in debug console.
So
"networkhashps" : 6943048374669430483746 / (1024 ^ 3) = 64.66 Gigahashes per second
It was the nodes part is not so obvious, btw have you noticed if this is accurate we only have around ~248 wallets online around the world,
masternodes =3222
active nodes =3470
hot wallets = 248
sounds too low don't you think, I am not sure I believe this figure, just the hot wallets for the exchanges and mining nodes must be quite a few for starters ..
I think this may be what you are looking for:
https://bitinfocharts.com/darkcoin/nodes/5161 Dash nodes
Anyway, this is just one site that may be using a specific method, just an indication I still think we should do our own official estimation. More than the amount itself I was interested in the relative comparison between Dash and other networks from the same site. So we may still need to do our own calculation to come up with an official number.