Hi Sally,
With regards to what to look for in a labs conformation etc I can't help really.
It is however VITAL that you check the bitch and sire have had their hips scored and ideally have a score of less than 20 ( I don't know what the lab average is and to be honest the lower the hip score the better). Also make sure BOTH parents have had the relevent eye checks for the breed. Making sure these thing are OK in the parents gives you a much better chance of saving yourself heartache later on with a poorly pup.
It may be that the dad is not KC registered and hence the price or it could be that this breeder can afford to sell the pups at this lower than average price for some reason and that both parents are registered. You need to be aware though that if both parents are not KC registered you will not be able to register the pup. For a pet this is not a major problem but please note you would NOT be able to show your dog other than at exemption shows.
It is making sure the health checks have been done that is major though as there are hereditery diseases with hips and eyes that can be passed on through the generations.
No injections is not a problem as the pup will have immunity from Mum and many Vets will not give the first injections till the pup is 10 weeks anyway. It is standard practise for a breeder to provide 6 weeks free insurance with a pup and I would strongly advise you keep this up as vets bills for minor things can turn out very expensive.
I'd suggest you
register with this site as well as "admin" prefer just one question to be posted per guest and then you can post on here as many times as you like :D
If you click on search and enter the words hip score it will bring you up a list of previous posts about the subject and may help you to understand what hip scores are and the importance of buying a pup from checked parents.
The pups should be bright and happy and willing to come to you. I would not advise picking a pup who is overly shy and does not like touching. At 4/5 weeks onwards they should be inquisitive about their surroundings and you.
I hope it all works out for you - please register and any questions you have post away on here. They are a helpful bunch who have taught me alot. No question is stupid - if you're not sure about anything just ask. We all started somewhere and there are quite a few people on site who have new additions or pups due who will be going through what you do (My latest addition is only 13 weeks old).
Look forward to speaking to you again and let us know if the checks have been done and you do get a pup from this litter :D
Sara