Dash removal 1996-2004 Mustang
IMO, the best step by step instructions on how to remove the Mustang's dash is in the Chilton's manual. It was a HUGE help when I did mine. Well worth the $$ for the pictures alone.
All of the Mustang's are similar with regards to dash removal (V6, GT, Cobra, Mach 1). Yes the AC has to be discharged to remove the dash. Remember to get a set of quick disconnect tools.
With regards to how much work it is. I won't lie. It's a big job with a lot of steps. However, it is not particularly complex just a lot of steps. It's also important to remove only the bolts called out in the instructions. It's not obvious which ones support "other" things. As said before, having the manual makes a world of difference.
It is a two man job to actually remove and install. IMO, it is easier if the front seats are removed. However, you will be surprised how few bolts actually hold the dash on after the steering column has been dropped.
Remember to disconnect the battery negative. There are tons of allways on circuits and likely to have problems if working with the battery still connected.
Consider adding leak check to the AC system. Inspect the AC core while the dash is out. If any evidence of leaking Freon is found, there will never be an easier time to replace the AC as well.
DO NOT buy an AC core from the autoparts store. Instead buy the service replacement from Ford. The $$ is about the same but most importantly, the service replacement has a new air box.
To use an auto store replacement, the air box has to be CUT in half and glued back together. The way plastic welding is done these days the chances of getting it apart without breaking it is almost nil.
The heater core is easy to access once the dash has been removed.
2003 GT Convertible (sold & missed)
2000 GT coupe (Craigslist project. Fixed. Now my DD). Windsor to Romeo swap.