ic. I do agree with what your mum said: Cakap omak kono la donga....hehehehe.... yes the n46 is the last batch of engine that was produced for e46. n42 (02-03, such as mine) is known to have issues with makan minyak etc, but with proper care and maintenance, alhamdulillah problem free so far. I'm not sure about n46 though. If the seller/owner does not know which engine the car has, you can check using VIN (vehicle ID number), thru realoem.com. it will tell you about the car, to a certain extent.
Interior wise, it actually depends on the trim/styling i.e. M-sport, lifestyle, executive etc. That determines a few thing such as steering (4-spoke, 3-spoke, M searing, multifunction), interior (leather or fabric seats, trim), body kits etc....banyak benda nk citer..... sorry la bro lagi penning jading. but more importantly, tgk condition engine and gearbox.
but end of day, think its your budget that will pretty much determine. if ada rezeki (combination of the right budget with the right car), dapat la apa yg kita nak....betul? All the best bro!