I agree, there isn't much that anyone with basic spannering skills couldn't do. I also do all my own work (all I say but admit some I don't have facilities or equipment for some things, like body work etc)
But do what you can, use genuine or equivalent parts and document what's been done to show its in line with the manufacturer requirements and it wont affect values or warranty.
Not that i'm mean but why should I pay £80-£100 an hour for someone to oil door locks or grease bonnet tapes for example??
I also actually enjoy the tinkering!

Steve