I've been playing a few hours and I died, but now when I wake up in the mortuary I cant leave. A portal used to open next to the ghost woman but now it isn't opening. How am I supposed to get out?

Since the portal is no longer opening, you must not have the portal key anymore. Looks like you'll need to get out through the front door. You could always ask for directions if you try to play it like you were just visiting.

Thanks for the reply but I don't think I can do that either. I read a walkthrough that said Soego opens the front door, but I already killed him. I ended up just reloading a save before I died.

If I remember correctly there is also a key hidden in the Mortuary that opens the front door. Depending on your status you'll have to fight the big skeletons guarding the exit, that could be hard depending on level and gear.

I couldn't find a key to open the main door (there is a key that opens all locked doors in 3rd floor). Killing everybody, or wearing a Dustmen robe won't change anything,

Thats a sad situation, usually people get the main door open at one point or another, or keep the portal key.

If you don't want to loose your time played, you can download a savegame editor

( http://www.sorcerers.net/Games/IEmodding/IESE.php , not a very convenient thing to use, you have to drag and drop the item to your inventory but it works, if one know a better one, feel free to share)

and use it to give you the Bone Charm which is the key to the portal.

(If you don't want to use a trainer but still have a recent save - before dying - you can buy the Charm from Mebbeth or one of the market's merchants)

If nothing else, could you try bashing the door down?

Hmm i did never try that, but I don't suppose that this will work. But he could try.

You can't bash doors that require a key.

IMO the easiest workaround would be using Tome o' Cheats (Qwinn's UB) to teleport yourself out.