Help. looking at a 1989 190E that has been sitting for over 6 months. One key, rotates in drivers door, lock knob doesn't move. Key doesn't turn in passenger side lock but does unlock the boot. Battery likely flat, but don't these have vacuum central locking? Will I have to break in? Is there a way to get the bonnet open from the outside only, and would a chargds battery make a differences.