Salaries vary widely here, International companies pay the best BP, Shell etc. I am not a civil engineer, but the advice I was given was ask for at least 25% more than my UK salary.
Also as for benefits - housing should be provided by your company (or money given to you to pay for a house/flat that you find yourself). You should also be asking for at least 2 paid flights home per year. Medical cover should be provided, and also schooling for any children you may have.
As for it 'not being a fun place to be', that is not quite true for all of us. The summer is great when you can go to the beach (finding a clean one isn't easy), and have endless BBQ's. Finding the right social circle to hang around with is also important. You will have a much more laid back time here than you would in the UK/US.
Scan through this forum, and you will see MANY differing views of life in Libya, some good, others bad, it is all down to how you approach it, sometimes I LOVE living here, other days I would pay money to leave. The good times out weigh the bad, hence I am still here.