Will it be possible to retrieve the body of our dead infant son for preservation?

Depends. Most facilities will work with you to provide a way to pay respects to your infant. The babies tissues begin to break down after death & delivery soon after a stillbirth will minimize distortion.Delays complicate the process.For postnatal death, the same process applies but distortion is less an issue.Please discuss your concerns with the nurses & facility staff ahead of time.
Most likely. I'm assuming you're referring to a baby who passed away due to an illness or still birth, and that's always a terrible tragedy. Of course your child's body will be released back to you for whatever burial or memorial plan you have arranged. Sometimes there can be a slight delay if there is a question to be cleared up in the death, and a medical examination is necessary.