They can be a bit of a pain to line up tbh mate mine took a lot of rocking the engine on a jack and some pry bar action to get it in. OEM LSD has a completely different shaped rear mount so not one of them.
I have a full list of what you need to convert if you want it. Auto is good in its own way as 2nd gear does 80mph so overtakes nicely. Now I am manual it is far better to drive though and handles far better. I still have auto clocks and auto ecu and both work fine.
I'm just going by pictures on here what the diff looks like so could be mate guess the only way to tell would be to split the box but that is too much hassle.
Depends how deep it is then you would need to find out how much is acceptable then measure it. May need a polish or worse a regrind/new crank, if it's only slight though maybe new seal just needs coat of oil so it's not dry.
I thought I would only need a friction modifier if the LSD was clunky and noisey? MT-90 doesn't have a friction mod in it but redline sell it on its own.