Congrats on you new purchase!
All ARs make that spring noise - its especially noticable if you wear earmuffs (as opposed to wearing ear-plugs). Grease on the spring WILL help - but I don't advise it as grease also atracts dirt.
Yes the spring should be lubed (with CLP). Right now I recommend you do the following
GO to
www.mcdl.org/Manuals/Manuals/Manual%20Depot.htmand download the -10 "M16A2/M4 Operators Manual"
AND READ IT as it covers operation, cleaning and lubrication. Then download the -23&P "M16A2/M4 Maintenance" so you have a reference for doing work on your rifle.
Your first purchases should be a decent cleaning Kit (like the OTIS or even a USGI kit), and get some Break Free CLP. Also you will want some USGI magazines (20 or 30 rounds). Skip steel magazines and even the plastic ones (unless you get a good deal on 30 round Thermolds). Skip any magazine made by USA. (you could read the Magazine FAQ in the Magazine forum for more details).
As for a trigger - if you really want a better trigger then go with the Rock River Arms (but use your current trigger and hammer pins - not the oversized ones that come with the trigger kit). I don't like the Bushmaster trigger as it uses set-screws.
Proper sight picture is for your nose to just about be touching the charging handle. Its tougher to do with the A2 stock and the fake telestocks - much easier with the older A1 stocks. For more info while you are at the above site download FM23-9 "M16 Marksmanship Manual"; read the first 4 chapters and appendix G.
Don't forget to come pay us a visit at
communities.msn.com/TheMaryland AR15ShootersSite