im planning to buy my rig tomorrow or this christmas eve at viewnet..it is better to assemble by myself or just let the shop do the assembling for me? need opinion here

will try to survey more..fyi, i got some experience with viewnet..last wednesday, my friend were buying a rig and viewnet staff are assembling it..after came back to hostel, i notice that, the driver cd of motherboard and gc was not there ..maybe they forget to put it back..who knows..