1994 Volvo 940 non-turbo 4 cylinder

I've had an exhaust type smell occassionally in the cabin of my car, recently I randomly popped the hood on a cold morning start and while looking around I noticed an exhaust leak between the manifold and the header pipe (down pipe ?).

I've got a new exhaust gasket (manifold to header pipe) 3 new studs and 3 new nuts to replace all from fcpgoton.

After a couple of days of soaking with PBblaster I crawled under the car and was able to twist, by hand, two of the 3 nuts loose. I'm wondering now if I even needed a new gasket, but since I have one and have new studs and nuts I figure its probably fine to just change everything out. The current studs are well rusted.

My question now that the nuts are off, how do I get the studs out?

Once the studs are out can I just pull down on the header pipe and slide in the gasket or do I need to remove more further down the exhaust system? If so, how far?

Can someone who's done the job before explain each step of the process? All hints/tips welcome.

And when all the new parts are in place, how much should I tighten the nuts. Should they be torqued or should I just crank them down as hard as I can?

Thanks for all the help,
liz

The picture shows what I'm working with and the dots may help you explaining what I need to do.