I really believe in stages would work well.
1. get the spare manifold down to KW who has kindly offered to drill/tap it for a reasonable no of beer tokens.
2. Spend one day max fitting the manifold and gas injector rail and 4 bits of pipe. This is basic stuff, nothing technical. Your car runs as before. Don't forget to clean the breathers before fitting !.
3. Fit the vapouriser and connect to the water supply to the carb and the output to the rail. Again nothing tech, just drill a couple of holes and fit a couple of bolts.
4. Fit the tank and do the pipe and solenoid/ gauge cable run. A bit of help would be a good idea here to get the best positioning.
5. Next finish off wiring and check/ commision everything.
The first 3 steps could be done easily by most Miggy owners capable of servicing, and to do the last couple, well a day, 2 max, provided all the bits were available.
Ken