Help: 1989 735i wont unlock

Happy new yr everyone. So im new to the bimmer family. I got a great deal on my neighbors 1989 735i. (he's older and hasnt driven it in at least 1.5yrs)

I have the keys but the car wont unlock. I can open the trunk but from what i understand the battery is in the back seat area. It obviously needs a jump but i cant get into the car to do so. How do i get the car unlocked?

What other basic things should i do as general tune up stuff once i get it open and charged? Dry gas, spark plugs etc. that you would recommend for this bmw model?

Thanks for your help.