Mine is pretty much the same components/ locations, except I use the BLOS mixer. Essentialy they come in complete kit form, no custom work really, but in the UK they have to be fitted by a certified installer, and it's generally a day or so for a simple mixer one.
The more sophisticated versions use propane injectors, one per cylinder, and are more efficient, but more expensive. Drilling and tapping the inlet manifold is a fair additional cost. The cheaper variant mix the gas into the airstream between the MAF/VAF and the throttle body.
And yes, you switch between propane and petrol at will (generally starting on petrol).