You might as well give it a try sneaking through to Nighon. You won't want to wait until you're strong enough to beat the Minotaur Kings in a fair fight before you finally make it there.

the trainers and merchants are definitely streamlined in MM8. a welcome change that isn't talked about enough.
and THAT is why you MUST take a cleric. there is a GM spell that prevents instant dead and eradicate effects on your party. I was sad to have to ditch my druid from MM6 but it was a necessary change

Yeah that's the flaw of the game, however it's still pleasant (and that's my prefered M&M).
These are actually 'quests' (you go after them), more than the main one as you say :)

Oh, I just remembered. Fun fact about the maze--there are places where the big minotaurs will get stuck in the wall, so if you can manoeuvre them into those little spots, you can take out the headsmen and the kings, without them getting close enough to even touch you. The little ones can still move around and attack you, but once you've killed a few of those, you can level to the point where they aren't a threat anymore. As I remember, all those together should be enough experience to get you strong enough to take care of the hydras.

It's also true of Thunderfist Mountain, but it's much much harder to do.

I've gone through at about level 5-10. Since I've played the game so many times. I focus on the challenge of getting the wizard and priest promotions very early on. With Invisibility it's snap maneuvering around the Minotaurs and Eyes.
Just put all your skill points into air and water.

Just one thing before making the trip buy a Town Portal spellbook.