I live in a 123 yr. old victorian home with a stone foundation. The old mortar is crumbling and of course over the years the house has settled leaving an uneven floor inside the house. How can I fix these problems: make the foundation secure and sound, as well as level the floor?

Hi Km,
You should first contact a foundation contractor and/or a structural engineer. Depending where the floor is unlevel, and the amount of deterioration of your current foundation, there is a broad range of possibilities. The home may be able to be jacked in the lowest corner and additional or secondary masonry would be constructed to support it at the level elevation. The mortar could be tuck pointed or if it's really bad (where stones are actually falling out of the wall) the foundation may need replacement. Just be sure before you start talking numbers that you research the contractor. Raising houses and repairing/replacing foundations is job best left to a contractor with the knowledge, experience and tools to get the job done professionally, efficiently and effectively. I recently did a house exhibiting some of the symptoms you list, and it's not a job to take lightly, trust me on this.
Andrew.