You know, I'd just call Glock and find an armorer in the area. Factory plastic stock sights are insanely cheap. My armorers manual is a bit old, but they lists the armorer's price as $1 for the front sight. Local PDs are good places to find armorers. Most of these guys are pretty cool and happy to help out if you explain the problem. Might charge you something like $5 to put it back on (takes just a few minutes). Most Glock stocking dealers have an armorer on staff. The cost of the sight just isn't worth shipping the gun back, unless Glock is willing to send you a label on their dime and you can live with losing your gun for about 2 weeks or so.
Night sights are real easy to put on yourself. I've done 4 sets myself (2 Meprolights and 2 Ameriglos). Best place to get Meps, I've found is OMB Police Supply. I just started using Ameriglos. Comes with the nutdriver you need for the front sight (screws in - just put a bit of red loc-tite on the thread, screw it down and make sure it's straight, let it dry). The rear sight on Ameriglos utilizes a set screw. Just knock out the old rear and slide in the new and tighten the set screws (it's a good idea to mark the position of the old rear sight and set your new ones there - should put you close). Go to the range, adjust for any windage discrepancies, then blue loc-tite the set screws. You're done.