As to the Qantas 380 event specifically, here’s the wiki on that model of engine:
What’s relevant here is the top two pictures.
Starting with the lower picture we see the man standing next to this beast, giving us a sense of the scale. Some of the stuff we see on or attached to the engine is test stand stuff, but most of it is part of the engine as it would be installed on an airplane. The intake end is at right and the front of the engine proper is about at the right edge of the black plastic sheeting. As installed on the airplane there’d be another 3-4 feet of cowling off to the right and then the lip of the intake.
The engine fuel shut-off valve is probably somewhere in that rat’s nest of gizmos and plumbing in front of the technician’s tummy & crotch. Which rat’s nest extends up the opposite of the engine about as far as it does on this side. So maybe from 4 o’clock to 8 o’clock.
The upper picture shows an engine ready to be installed into the nacelle and hung from the pylon. We can see where the engine proper joins the white intake cowling & lip. Up at the very top by the red box we see where fuel and hydraulic lines and wiring connectors wrapped in sheet plastic and blue tape will eventually connect to the pylon and the rest of the airplane. I bet the largest and rightmost tube is the fuel line. Just below where the lines run horizontally forward is a tan-ish box with a yellow cylinder attached to the upper aft side. The yellow cylinder is the oil filter and the tannish box is the oil tank.
From the other picture we get a sense of scale; the fuel line is about the cross-section of the man’s wrist and the oil tank is a couple feet above the man’s head and maybe 3/4ths the height & width of his torso. Although he’s a bunch thicker than it is. 
From @Francis_Vaughan’s picture of the fire/rescue folks trying to stop the engine (post #8) we see that as installed the bottom of the engine cowling is some 6-8 feet off the ground. That’s the outboard engine. The inboards hang a little closer to the ground, say 4-6 feet.
It’s also worth noting that as large as the Trent 900 is, the very largest turbofans are about 25% bigger in size and power output.