To answer your to points.
1.) I would suggest that you do some more research. This forum has a bunch of great threads on feeding in an out of the snakes enclosure.
2.) Ingesting aspen is not likely to cause any issues. In the wild (not saying all things in the wild are good) snakes will routinely ingest things that get stuck to their prey. If you are still concerned what you can do is place a paper towel in the cage and then feed over the paper towel.
At the end of the day its all up to you on how you keep your snake. I merely wanted to suggest that feeding in the cage is a real option that many many keepers practice with no ill effects.