I have the chiltons manual and it does a good job of explaining step by step what to do, although it is broken up into sections (i.e. one section for removing the cover, another section for removing the belt, etc.). Looks like the only special tool that is required is a balancer puller to remove the crank pully. the other thing that can be difficult is removive is the bolt from the crank. depending on which way the motor rotates, you could put a breaker bar on there and tap the key to loosen it. i have done that before for other cars.
My wife has a 95 Mystique with the Zetec engine and it has about 110K miles on it. The car died on the freeway on friday. i peaked under the timing cover and had her hit the key and i could see that the belt was not spinning so i assumed that the belt broke. I just got through putting in a new cv shaft and ball joint and i was not up to doing any more work myself on the car just yet so i sent it out to be fixed. It cost me $165 for labor so at that price i thought it was worth it for me not to hassle with it. the belt was $23 at Advanced Auto Parts/Part America.
I found out however that the belt did not break, instead IT WAS THE TENSIONER THAT FAILED. I guess the tensioner must have been binding some so when it was torn down the mechanic found the tensioner pulley was broken in pieces. That was a dealer item and cost me $73! Believe it or not the belt lived through this! Since it was apart I had the new belt put on anyhow.
Anyhow, the good part of the story is that there was no engine damage and after repairing the belt/tensioner the car runs good again. The Chiltons manual claims that it is an interference engine but i think it must be wrong. For one, Ford does not have a recommended replacement interval which I think they would if it were interference and damage could result, and the second reason is that
www.gates.com does not list it as an interference engine.
If you can handle the inconvenience of being stranded when the belt breaks I say wait for it to break then replace it - no harm done. If not, I'd say replace the belt and tensioner at about 100K miles. I have heard other people on this forum complain about the tensioner breaking. Assuming the aftermarket belt is as good, replace the next one at another 100K or replace it at 75K if you feel it lower quality.