Manual essential. The locks operate by operating the driver's door button - that works the others. Get the hand book too - I got mine E-bay. Many questions asked here are answered in the hand book. Read, mark, learn and inwardly digest. Pull the door cards (trims) and lube up the locks with WD-40 or whatever good similar spray you genrally use.
Good - Fast - Cheap: Pick any two.
E23 735i; E30 318i; E32 735iL (X 2 - 1 Alpine White and 1 Glacier Blue); E34 535i; E38 735iL; R50 Cooper; R55 Cooper Clubman.
E21 318i; E32 735iL; E34 535i; E38 730iL; E53 4.4i