Today I removed my 5HP 24 gearbox.
What a total PITA it has been.

Every nut, bolt and fitting was so tight that I struggled even with a breaker bar.
2 hours to get the 3 torx bolts out of the left cat heat shield, they are in such a stupid place.
2 hours to get the exhaust off, snapping 3 studs holding the cats to the manifolds along the way.
90 minutes to remove the transmission cooler pipes, chewing up the fitting to near unrecognisable.
Snapped the bottom 2 bell housing bolts clean off while removing the cat brackets.
The 3 torque converter to flywheel bolts almost defeated me.
The prop shaft fittings took 30 minutes.
Surprisingly the transmission carrier came off straight away.
The remaining bell housing bolts needed the help of a breaker bar, most of which required wedging myself under the car and pulling till I lifted myself from the floor.
Separating the tranny from the engine took 40 minutes due to the aforementioned snapped bolts being completely corroded through the bell housing.

The car was left all week and was sprayed liberally with WD40 several times.
I have a nice workshop with a mid rise scissor lift etc so I mistakenly thought I was going to have an easy time.

All I have to do tomorrow is figure out how to remove the 5 snapped bolts that have so far resisted all attempts at removal (2 cans of propane and 3 cans of WD40) and I can put my replacement transmission in.

Did I mention dropping the ratchet and cutting the bridge of my nose to the bone while coolant dripped into my eyes?

 

Sorry to hear about all your problems. I had some difficulties on my first transmission(gearbox) removal. I broke a few of the exhaust studs like you did. So now before I loosen any bolts or studs they get a good soaking of PB blaster. You'll have to get aftermarket studs. When my broke I went to the local Jag dealer . They had the nuts but to get the studs you had to buy the cats. I told him no thank you.
Suggestion: When you reinstall do no put the exhaust studs in until the cats are in. My first time I was trying to get the complete exhaust in and couldn't get the cats in. After fighting it for over an hour and after a pry bar hit me in the head l said to myself, dummy take the studs out. I did that and went right in. I also found to put the large heatshield on the exhaust manifold from the bottom before installing the exhaust. It is a PITA to try to get it in afterwards. If you have anymore problems post it and get help from the forum. GOOD LUCK.