Call Glock Technical Support in Smyrna, GA. (1.770.432.1202) Give them the serial number of the G-17 you've purchased; and they will tell you whether or not a recall applies to your, 'new' pistol.
(I do think that you'll, probably, end up with some version of Glock's infamous, 'Six Part Upgrade'. If so, I suggest you find a local certified Glock Armorer to install all replacement parts for you. This armorer can, also, breakdown the pistol and do a thorough inspection along with any obviously necessary parts change.)
If it were my recently acquired (and used) Glock pistol, the very least I would do is to replace every spring in the gun with a brand new and equivalent Wolff Gunspring. If you want to change to a 4.5# connector, (There is no such thing as a, '3.5# connector'; it's an advertising misnomer.) I'd further suggest that you switch to a Wolff Gunspring's 6# trigger spring, too. Do NOT, however, attempt to lighten up on the striker spring. Keep your Glock safe by staying with the factory standard 5# FP spring, or heavier.
Lone Wolf Distributors, and Ghost, Inc. make two of the very best 4.5# aftermarket connectors. If you make this change make absolutely certain to load only two or three cartridges at a time, tightly hold onto the pistol, and TEST FIRE it for proper function BEFORE attempting to use the pistol as you normally would.
