Get another opinion and by someone who knows newer Volvos (like yours). There is no oil pan gasket, it's a liquid gasket and it rarely ever leaks in itself unless the pan's cracked from damage. If the pan does need to ever be removed, it can be done w/o pulling the engine (rediculous!). It's more likely that something above or behind the pan is leaking, like the turbo drain tube o-ring (common and inexpensive to repair) or worse, rear main seal (tran needs to be removed). With higher mileage, sometimes the front oil pump seals also leak (also time consuming).
I'd gather that your "mechanic" doesn't know Volvos and isn't interested in repairing your car either so find someone else.