I think it should help matters if everything's warm, but probably doesn't make that much difference.
Do you have some long-ish extensions for 3/8" square drive socket stuff? Undoing the 4 bolts that hold the downpipe to the manifold is mostly a 'from beneath' job, which will be much easier if you have some extensions that you can bung together in various combinations to get a few different lengths. Jack and support the front of the car reasonably high to give yourself space under there too.
Be safe, use axle stands, and chocks round the back wheels ideally, as well as a firmly applied handbrake.
There's one of the four bolts you have to (un)do from the engine bay IIRC, no clear path to it from beneath due to the shape of the downpipes
Get some PlusGas on all the manifold nuts/studs, and the 4 bolt threads of the manifold/downpipe connection now, then again tomorrow. With a bit of luck everything should undo nicely on Friday then.
My last piece of advice:
if the broken stud is more-or-less flush with the face of the head (i.e nothing to grab/weld to)
take your time getting a good centrepunch mark
right in the centre of it before you do any drilling for the easy-out. Then get someone to watch while you drill to try to make sure your hole is nice and straight, right up the middle of what's left of the stud. If you go off centre or off straight, it'll make life much harder for the easy-out. Oh, and don't drill too deep! Look at one of the new studs, and mark your drill with tape for no further than the end of the stud. You really dont want to be drilling into alloy beyond the original hole.
Good luck.
