I don't recall that Mythril Bar to be difficult to find. The dungeon where it is, is pretty straightforward, IIRC (it's been awhile). There are a few places where you're faced with locked doors/gates, but the levers/keys that open them are easy to find. Just explore a bit. IIRC, everytime there are two doors or the corridor forks, one of them is locked and the other leads to the opening lever/key (and is a dead-end itself).
Spoiler about the last room of that dungeon...
There will be two noximanders waiting for you in the last room. These can be a bit tough on new characters, especially as their bite is poisonous. Bring Cure Poison (or whatever they were named) potions with you, if you can. And remember, you don't have to kill the noximanders, per se, you can just run past them if you're careful or you can let the dungeon do the killing for you...
It is pitch black. You are likely to be eaten by a grue.
And remember that some barred areas won't open unless you step on a particular floor section. Sometimes it's difficult to find them and sometimes what you think is a pressure plate to open a door is really a trap!
