If you have a hoist like the others said then most of the work can be done in little under a few hours.

The MK3.5 had this engine in it aswell so its not complicated. Put the engine and gearbox together and put it in from the bottom. On the loom all the plugs are different from each other so its easy to know here they go and the water plumbing won't take you long either.

The first quote you got sounds more realistic from any normal garage that isn't BMW or Aston Martin....