I had the same problem when I was baking banana bread - dark, hard crust. I started experimenting with lowering the temp a little and raising the time a little. I now know that I need to lower the temp 15* and add on ~7 minutes. I now have a nicely done loaf, baked all the way through with a nicely brown crust which is somewhat crisp on the top but soft and firm on the sides.
HTH
ETA - you really should be able to substitute liquid shortening for solid shortening without a problem. I have substitued cooking oil for stick margarine before and have never really had a problem.
Your best bet would be to go back to the receipt as written and start over.