You should definitely spray those nuts with penetrant before trying to crack them. Maybe hit them with a wire brush first, and do several applications of penetrant over the course of a few days. If you have to put any force on the nuts, try tapping on the ends of the studs with a wrench or something and apply more penetrant. Those studs will be brittle, and they are even harder to remove when broken. I went through every size of left handed drillbit when I broke one and it still wouldn't back out.
If the stud spins out with the nut, count yourself lucky and don't put it back. Buy new studs and nuts. Buy bolts instead if you have to, just don't try to reuse the old hardware. Tap out the threads (probably 8mmx1.25) in the housing if you end up with that much access. If the stud doesn't come out with the nut and looks like it would put up a fight to the death, don't push your luck unless you have lots of time to carefully manipulate it out on the bench.
If you get the temptation to remove the studs anyway, spray them with penetrant in the holes where they thread into the housing and try to (carefully) bang on the ends a bit with a drift through those holes. If the penetrant comes out rust colored after doing that, you have a better chance. If not, it's probably welded to the housing.
If one of the studs has to be removed because it it's bent, count on having to remove the turbo to work on it.
You might have no problems at all moving the fasteners, but please approach them carefully. I didn't once, and it really sucked. Hours of pressing on a drillbit soaked in ATF.
