I would either talk to my local Honda shop (most shops are pretty cool about helping out someone with a little bit of info-just don't overdo it on getting some free info) or buy a manual here: http://www.atv-411.com/honda-atv-repair-manual-9.html
Yes it does.
I clocked my 1987 250x at 62mph using a friend's car following.
no you dont have to its a 4-stroke it runs on unleaded fuel no mix
NGK Makes Really Good Spart Plugs.
It is a 18 mm socket that works to get the spark plug out, it took me a while to figure it out.
It's not too bad you need to get the engine at tdc and then check the flywheel marks through the timing hole. Check out my bio page for help.
10w-30
not fast enough
60
10 w 40 is what honda recomends
around 60mph
1.5 quarts