Thats the right diff, you just need the matching pinion and bearings, and a few 10x8x0.2mm shims/washers to set the mesh correctly- given the shipping costs from the usa to sweden, it would probably be cheaper to buy the diff kit from Mike, that way all you need are the shims.
Ofna diffs will fit too, but I dont think the V3 revo ones will as they are narrower.
All the 3905 parts will fit the FLM 3905 chassis- tranny, receiver box, steering mechanism etc.
You should only need to put one or two shims behind the head of the pinion gear, between it and the inner bearing to set the pinion depth- shouldnt need to put any either side of the diff to center it, but you will soon see if they are needed once you start assembling the hybrid bulks (different people experience different requirements due to minute differences between the bulks and diffs & bearing etc).
I have a tutorial of sorts on assembling 1/8 scale diffs- I used UE diffs, but the same principles apply to the hybrid bulks:
http://www.rc-monster.com/forum/showthread.php?t=8012
If you want to use the stock drive shafts or cvds, you will need to purchase those output shafts and swap them over onto the diffs, otherwise poeple find the stock drive cups to be a bit shallow for most cvds (you can always find deeper drive cups though, depends what you plan to use really).
For 4 shocks, I would use for ofna truggy shocks- also sold as super shocks by UE (though UE dont sell outside the USA so you will have to look around for them- ebay).
Not a cheap hobby for sure, but jusr point out the wife's dress, jewellery and shoe collection, Im sure she'll be a bit more understanding then...