You help one neighbour with their car and it snowballs.

I don't want to turn this into a long drawn-out discussion, nor hijack this tread, BUT
Just keep in mind that you are not a Licensed Auto Facility with Professional Mechanics (not sure in Canada) and its possible that you can be sued if there is an accident.
Here in the states, once an insurance company finds out a "friend" performed repair work they will try to deny the claim and the other party will try to sue especially if injuries are involved.