4.6 hse petrol (lpg)

hi all first time on here.. got a 1996 p38 went to other night completly dead. charged upbattery now fob wont work done eka code still wont start keeps saying engine disabled, key code lock out.. i will be getting a local firm out and i was wondering will they be able to plug in with there lap top at my house and re-boot everything and also get my fobs working again? Should i get a new battery too? any advice/answers gratefully welcomed just so i have a bit of ammunition when they arrive at my house.. finally anybody have any idea how much this is going to cost me?