As Carbonazza says, changing out a pressfit BB shouldn't be an issue at all with the right tools. I don't know how trivial it is without the specialty tools but it's doable. I have the Wheels MFG version of the threaded press fit and it's absolutely the...best...thing...ever.
Your spacer and handlebar issue though...
Once you cut your steerer tube down to size, that's it, there's no going back. The TanTan handlebars came with around 4 cms of spacers and I use all of them. My steerer is cut 3 mm below the top of the stem and I still have to use another generic round 2mm spacer I picked up from my LBS on top of the stem, just underneath the top cap, to get the head tight enough. Maybe if you can figure out a way to stack 2 cms+ of generic spacers above your stem until your set arrives, you'd be able to cut the steerer to the correct size and get riding. It'd be fugly though, and judging from the generic spacer I use, not a very stable stack on top of your stem.