Buying a second hand car in Malaysia is as risky as any other country so the rule is caveat emptor (buyer beware). A few things to consider:
When it comes to selling cars you can either go to a dealer and get a (usually) lower price or you can try to sell it yourself. If you are making a private sale then you should try to find another partner as there are always some risks in having strangers come to see your car. If they want a test drive you better make sure you go with them and it's safer if there is only one of them.
It's best if they do not come to your home as this may put yourself and family at risk. The other disadvantage of selling yourself is that if the buyer is looking for finance there may be delays in finalising the sale at a time when you are trying to wrap things up quickly before you leave the country. It's usually a lot less hassle to sell it to a dealer.