bro, firstly, u need to identified a reliable specialized bmw workshop to answer all your question. the mechanic is the best person to advice u on the parts condition wether to change or not..
the main basic important parts are to change the all the radiator hose,coolant,waterpump, brake pads,service all the oil: engine oil,axle oil,gearbox oil,brake oil,power stering oil,spark plugs,fuel filter,aircond microfilter.. and wheel alignment.
this services above will ligthen ur wallet oredi..that's why its very important to have service records frm previous owner regardless frm used car dealers.
its better to use ur extra budget for new mod..
all the best to u bro..
ps:
328 using timing chain and requires u 8 liters engine oil and 6 spark plugs.