1974 Chevy Impala

so i'm trying to be a nice girlfriend by helping out my boyfriend. he just bought a 1974 chevy impala that has be somewhat restored. has a 350 engine. i guess its a two barrell. umm new paint job ne tires and rims. the thing is he wants to finish fixing it up. so i want to help and do as much as i can but i know nothing about cars. i know that it does have a problem with starting and the battery had to be charged again before he could get it up and going. does anyone know what type of battery he would have to buy to put in the car? also i would like to know what type of oil he would need since the car is so old and would eat up any of this new thin oil thats on the markets now. please help me! lol