The Model-T ford was designed to be largely user serviceable. The model T came with a user manual that allowed someone with minor mechanical skill and basic tools to perform a lot of repairs. The manuals that came with the car covers a variety of "Points on maintenance" questions as well as more advanced repairs.

For example, the 1914 owner's manual answers questions such as "what is the best way to fill the "Dope" cups?" and "How often should oil be drained from Crank Case?" There are even sections on removing the front and rear axles.

But, your Model T has broken down! The 1914 manual covers common causes of engine trouble and gives lots of tips for repairing parts without replacing the part. However, if a part is truly irreparable you'll need the Price List of Parts and Instruction Book (1909 example here). Using that, you can look at schematics of the car, find the right parts, use Ford's handy Telegraph Code to order mail-order parts and follow the instructions to do repairs. The section on removing the rear axle gives an example of the kind of knowledge and tools Ford expected the person servicing the car to have:

Jack up car with heavy bar on two horses so that wheels hang free. Take out four cotter-pinned castle nutted bolts connecting two halves of universal ball collar. Disconnect brake rods. Remove rear wheels by unscrewing hub cap using special hub wrench furnished with the car. Drive out pin, pull out key with pliers, pull off wheel...

As an aside, the manual's authors appear to be assuming the user knows how to "disconnect brake rods." I can't say how intuitive that task is but I did use the manuals for my Model T (my father's at the time) to gap the spark plugs and fix an issue with the radiator. At ~16, and not particularly automotive adept (I've never changed my own oil), I was able to use only the manual any my intuition to figure out what was needed when the manual said things like that.

There's even a section on unusual circumstances after you take off the rear axle. As if taking off the rear axle isn't unusual enough...:

If necessary, and it is not under ordinary circumstances, to dis-assemble differential gear, a very slight mechanical knowledge will permit one to immediately discern how to do it once it is exposed to view. Care mus be exercised to get every pin, bolt and key back in its exact position when re-assembling.

Of course, you might think you can take your model T to a dealer to have it repaired. There are dealer repair parts lists for ford parts and "Not Ford Manufacture" parts. However, the Model T was the first mass-produced car and it started production in 1909. I will leave it to others (with more complete sources on the development of the auto mechanic industry) to say how well established the "car mechanic industry"was in the 1910's. The Machinists Union formed the first automotive Local Lodge in 1912 in NYC so there appears to have been a developing network of auto mechanics in the 1910's. However, I cannot say how widespread that industry was and how much it was used as opposed to taking your Model T to a bicycle mechanic, machinist or blacksmith for help.