I always wonder about these questions "is it cheating if I..."
What does it matter?? If you can't even tell whether it's cheating beforehand, then what does it matter if it is? Hey, for some people, even SAVING the game is cheating, because you can't do that in pen and paper AD&D either. Just do whatever YOU consider to be a fun way of playing!
As for soloing, are you sure? You'll miss out on a lot of romancing and fun little quests and conversations. Most people that solo the game only do so after they get bored with playing the game with NPCs. Still, it's up to you, I suppose.
Like Regin said, the difficulty depends on what kind of class you play. A jester would be...daring
Remember that you need someone who can cater for all your needs in the game, so if you aren't a thief and cannot disarm traps, you either need a fighter who's so tough that he can just walk through them, or a mage who can send summoned critters to set off the traps, etc.
You can also start a multiplayer game without connecting to the internet. Then, you can create two of your own characters (to make the 'solo'ing slightly easier) and play with them.