Cragius,
First off, that's an excellent price for an already clipped and pinned German G3 type SEF housing. Boy, I remember the good old days 10-12 years ago when I offered this service. The housings were running $100+ back then and I charged $40 to clip and pin.
For what it's worth, the pins going left to right are actually done that way tactically on purpose. It's meant so the operator doesn't confuse the push-pin with mag release on the right side.... now, it's your lower and your weapon so you can definitely do what you want by all means... The pin is merely cosmetic so you can easily tap the ends out, swap and reglue them around if you'd like. Any clear expoxy will work well.
Good luck and I think you did very well on your purchase
Michael
Law Enforcement Sales
Oak Ridge, TN 37830
07/02 FFL/SOT