Not sure if the earlier cars (pre facelift) had less space but on my 06 S60 have had to change the headlamp bulbs many times, it can be done but def isnt easy, top tips below... Assuming you have the 'plug' pulled off (that bit not too difficult)
1) use a mirror to get a view of the spring wire clip thing, then open it with some fiddling, remove old bulb BUT.. note where the 'key' is (from memory at top?) as you need this for getting new one in blind.
2) use some masking tape, on your longest middle finger and tape the new bulb so its loosely held (but can be pushed off with another free finger) with
the key in right orientation.
3) carefully get the new bulb into the headlamp (use a torch from outside headlamp gives you some clue if your in the right place, and the bulb fully home into its location (key at top?). Now push the bulb away from the taped finger and it should stay in place and remove hand ! phew almost there..
4) carefully move the wire spring retainer over it and get the end hooked under its channel before releasing (at this point, spring trouble often goes with the bulb getting out of position) so take care, to avoid going back to step 3!.
With luck, if all goes well, your done ... can take anything from 10mins to and hour or 2 if you get your hand stuck
Ive been using osram nightbreakers for years but they don't last as long as 'regular' H7 bulbs (probably true of any brighter halogen/xenon bulbs) so the need to find a way to swap them is required .. what does that phrase go...