Those are indeed pressed, or on some models actually spotwelded in place. After being disturbed, you can bet the gasket is now damaged and will need replaced also.
Studs will both need replaced.Usually have to be heated near red with a torch. Since you have no tools or decent place to work, expect to take it to a shop and pay no more than 1 hr. labor, 10-15 bucks for a gasket and a couple more for bolts. At my shop I'd expect it to run approx $50.
best,
Bob