IMO, if you can boil the full volume you should do it. But great beer can and has been made with a concentrated boil.
Neither of the two issues pointed out above is specific to extract, really. A concentrated boil will decrease hop utilization but that can be compensated for by using more hops. If you don't have an immersion chiller you can always just put your kettle in an ice bath. The quicker you cool the wort, the better, but there are people on this forum who have cooled over night and pitched the next day. IIRC they put the covered fermenter into a lagering fridge or something like that. Not ideal, but with great sanitation it can be done.
One thing to consider is that with extract and a concentrated boil you may get more darkening of the wort than you would with a full boil. This is also easily compensated for by adding a significant portion of the extract late in the boil. This approach works well for a concentrated boil, as you keep also keep the initial gravity of the wort lower and improve hop utilization. If you do not go for the full boil, I would recommend that you add at least 50% or so of your extract late.