Well.... it's probably a C20XE with an F20 but you had better make sure.... can you get some engine/tranny pictures from the guy?
Too bad it wasn't a C20LET (2.0L 16V turbo) with an F28 (6speed AWD)
You need to research Astra MkII conversions as this is the same as the Lanos chassis.
You will need the front engine mount from an 2.0L Astra MKII (europe/uk) or 2.0L Pontiac Lemans (north america)
Wiring is the main issue.... the C20XE should be nearly self sufficent with respect to engine wiring..... there should only be a couple of wires to hook up.
I would keep the Lanos ECU in place to run the ABS and all the other systems such as the tachometer.
You will need to keep the Lanos drive shafts and the lanos brakes..... the Calibra uses a totally different bolt pattern (among other things)
If you want to upgrade you should talk to Tom@360D as he's very familiar with Astra MKII and Lanos brake systems (where as I am not)
Basicly... If I were you and all you want is a C20XE.... I would keep the stock D16 tranny of the Lanos.
The F16/D16 are nearly identical to the F20/D20 ..... the 20 series have stronger internal parts.
Externally.... they mount up exactly the same.
The problem with using an F20 is that the clutch is cable driven and your lanos uses a hydraulic system (which is the main difference between the F20 and D20 )
You could convert it over but that might be a pain.... I don't know as I haven't done any research on what is involved in converting from cable to hydraulic ( or vise versa)