#0 youtube is no good for modding anything. don't support piracy, buy legit games and rip them to your harddrive as you will go for a softmodding route with external usb drive
#1 not hard but challanging. take your time to read everything carfully. use the softmod any wii guide (link below) and you will end up fully softmodded.
#2 DO NOT Update through nintendo. also there is no need to update anything to play any specific game or something. (updating through nintendo or handling the right tools the wrong way can brick you yes -> get measures to keep the risk as low as possible (priiloader/bootmii))
#3 yes. also recommended to keep the softmod up to date (but only really neccesary if you run into errors) again: no need to update the wii, do softmod guide and end up with version 4.1 and stay there (nothing special at all on 4.2/4.3 no benefit for the user at all)
#4 yes. (for a chip you have to open the case)
#5 messing around getting all that stuff running. but its worth. you'll be amazed when done (game loading through nice coverflow loaders (check wiiflow on youtube), mediaplayer mp3/avi/dvd)
#6 softmod. its for free. so much more options to tweak with (usb loading is the best, game collection on one drive (i know wode can have that too) oh and it is for free
#7 had to solder the oldschool wiikey1 to the drive board. really tricky. it got better with solderless chips, wode etc. updates around. if you get errors you will do a slight softmod route alongside sooner or later..
#8 use your retail discs (which will get scratches on them) and arrange them nicely in your shelf.
#9 so many questions man just browse the forum, look in the recommended guides section. read the newbie stuff. you ll figure everything out I am sure. reading means the next days not for half an hour
modding also does not interfer with online playing (cheating excepted)
edit: new wiis are on 4.2 if you are lucky or on 4.3, meaning you will also need lego indiana jones or smashbrosbrawl (depending on the region of the wii, european or usa, covered all in the guide, you can already start reading)