Don't hesitate to go back to the shop for any issues you have with the new bike. Especially if it's in the mid to high price tier. But even the lowest price tier bike should go back when things don't work right in the first 3 to 6 months. Maybe more.
It's great if you want to do your own DIY, but on brand new bikes, you should limit that until it gets to the point the shop starts charging you for every little thing, or you wear out your welcome there.
When shops do something free for me, I usually buy a pair of gloves, socks or something else I can put to good use.