I tried to keep my response as generalized as possible, because in Canada it is getting more and more difficult for the 'backyard' mechanic to be able to do anything on a vehicle. I can see it may end up somewhat like the aviation industry - you will not be able to modify a vehicle in any way, shape, or form, without the signature of a licensed mechanic or a mechanical engineer.
The autobody industry is already at that point - if any insurance company writes a vehicle off, no one but a certified body mechanic can salvage it and put it back on the road. There is even a notation that gets added to that serial number stating that it has been salvaged.
The complexities of computers - as many as 20 on some of the newer models - also makes it more difficult for a 'backyard' mechanic - unless they are willing to invest in the diagnostic tools that will allow them to troubleshoot an electronic defect indication.
But for all the above reasons - LIABILITY will be the biggest deterrent to anyone trying to maintain their vehicle. Even now I am exceeding careful about what work I am willing to undertake - no one but close relatives and people I have known for a long time. Gone are the days when we could do a quick once over and sign off an insurance inspection. Here we cannot even build a trailer without taking it to an approved inspection center for certification and a license plate, plus up to $400.00.
The government is just taking all the fun out of working on your own stuff.
There - that is my lament.