There are many shops in sim lim. Its better if you take a person who knows sim lim shops pretty well. Have experience in buying DIY PC. Me always go to costronic. But some say their service not good. I am buying from them for the last 4 yrs. Even for office we buy from them.
If you newbie, dont know anything about hardware parts better buy a branded PC. Nowadays dell computer ,we can get for less than 1000 dollars.