Not easy proccess. No bank gurantee but difficult and long process. Better to visit any importer and ask him to import for you.
On auction sites you need to register by paying some amount like 1 lac and then take part in auction. after buying car the sign up cost will be adjusted. then you pay them some charges to import your car to pakistan also. then you need clearance from customs which is difficult job too. it may cost you more than you buy from any dealer.
i don't know about any websites either good or bad.but trust me it's headache