It can be done without pulling the engine or lifting the cab,( My dealer is doing it now to my wifes Excursion) but they had to remove the ac plenum on the pass. side IMHO It would be faster and easier on the back to pull the engine. Unless your an experienced tech, dont even think about attempting this job, If you make a mistake it could be alot more costly than having it done by a pro to begin with.Good luck and keep us posted.
That's right, I had forgot you had an excursion, I would say best bet is to pull the engine, some have attempted it without doing either of what I had mentioned, but I believe it's going to be easier to pull the engine. I wouldn't do it myself, but I'm not all that comfortable to doing that kind of job on my tractor(tractor maybe with a manual) but not my truck.
If your leaking coolant, your heads are more then likely warped by now, if you don't machine the heads(if it isn't too bad, otherwise you'll have to replace the heads) then all this is for nothing because you'll have to come back later and redo this all over again(personal experiance right here). That is probably would it would cost a shade tree mechanic to do it and you would get studs which is far superior to the ford bolts.
If worst comes to worse, I would think the dealership would install the studs for you, rather or not they will take the heads to be machined depends on how they do things like that, but it's all on your dime so I don't think they would squawk all that much about it.