Originally Posted by
morgothaod
I'm trying to make my mountain bike more comfortable by giving myself a more upright riding position.

I have a Specialized Crossroads from the '90s, similar to your bike, but with 700c tires. I raised the stem as much as possible, changed my handlebar to one similar to your "top" picture and changed the saddle to one more suited for upright riding. What a difference these "small" changes made! Not quite dialed in yet (I'm playing with my seat fore/aft), but getting there.
I had the saddle and paid the LBS for everything else. They were able to move my grip shifters and didn't need to change any of the cables. I think the bill came to $70.