If something went wrong with your Giant it wouldn't be too difficult to get it back on the road - bike parts and spares are pretty easy to come by even in the most obscure reaches of Romania et al - BUT, you would have to accept that you will probably not be able to get like-for-like spares - you'd have to go out accepting that your SCR 3 might not come back looking quite like an SCR 3 - wheels, tyres, gear mechs...whatever goes wrong you will just have to settle for whatever is on offer at the time and potentially ditch your slightly broken original parts (or lug them to the next post office or whatever).
If you're happy with that then fine, it's perfectly feasible to do it on your Giant in that respect.
The other issue, however, is weight. I personally wouldn't do such a trip on an out and out road bike. The weight of a camping load, combined with the sections of rough road/potholes you will undoubtedly encounter is not a good combination for such wheels, in my opinion.
If I were you I'd forget about upgrading, keep your Giant as a road bike and try and get yourself a tough, easy to repair alternative. 700c or 26" wheels is up to you - I did it on 700s (x32) but when I do my next trip I'll be going on 26". You could probably source pretty cheap parts from various places and even if you have to spend a bit of time on putting it all together it'll be good practice for running repairs when you're out there. Stick a rack on the back, a couple of roomy panniers, a drybag across the back and a barbag on the front and you're good to go!
Having said all that, don't get too anxious about all this. Sure, it's worth preparing well and knowing your gear, but when you're out there it's not as if something suddenly changes and you're extra vunerable to bike failure - it's just like riding around wherever you do at the moment really, expect it'll all be new. You'll get punctures, maybe a cable will break or a tyre explode (mine did, twice) but if you have enough spares with you to botch it to the next town you're alright. My rear hub shattered somewhere in Italy, spokes rattling around all over the place, but I managed another four days/200 miles until I found a decent bike shop who had an adequate replacement.