exhaust for 95 LS

ok i just recently put on a new AEM CAI and now i am interested in the exhaust. my friend has an APEXi muffler he will sell me but i don't exactly know much about all the custom piping and crap. my dad has a friend that owns a muffler shop but i don't exactly know what to ask them to see if they do custom piping. what should i ask about to make sure i am getting the best for my teg? i just don't want them to slap the muffler on and defeat the whole purpose i am looking for. can anyone give me some guidance on what i should do?