[AceX]

The speaker should just screw in like the stock piece unless you got a different size speaker than what came from the factory.

If that's the case, head to a local stereo shop. They should have an adapter plate of some type to help you.

As for the rear support piece, epoxy won't work. This unit will have to be well secured. If you have to, go find some flat aluminum at Home Depot or where ever and bend it to fit up to an existing bolt under the dash. Drill a couple holes in the new bracket and replace the target bolt with a slightly longer one.