Introducing an older dog to a new puppy?

[eyeofhorus28]

Hi,
I have a 2 year old rescue dog that i got from the local kennels.Ive had him a year and hes amazing.Hes a cross collie with an unknown terrier,a little bigger than a corgi.The vet isnt sure what hes crossed with,and neither was the kennel.I am collecting a 6 week old labrador puppy on friday, (male)and want to know the best way to introduce them.My 2 year old has size issues with other dogs,if they are bigger he will sometimes growl,and bit a bit agressive,but with smaller dogs hes ok (and can get a bit rude,hes not castrated lol)im worried he might growl or snap at the pup.Any advice greatly appreciated on how to bring the puppy into his territory.Many thanks.
Reading through all your answers and taking in all advice.I have a safety gate as my dog is allowed to free roam my house,hes never chewed or peed in the house,but i dont like him going upstairs.The breeder has told me that the lab has been weaned last week due to the mum refusing to feed them (litter was 13)i made sure i saw them using the toilet for signs of diarhoea etc,and i myself thought that maybe 6 weeks was too young,but shes assured me that its fine.I also bought a crate/cage for my older dog but he never used or i didnt make him use it so i have a crate too to put him in.You think 6 weeks is too young for a pup to be away from its mother?thank you all so much