foam rubber material on firewall.
 

The sound deadening material on the firewall of my '86 has separated and is basically leaning on the airbox, etc.

Is there a standard fix for this? Removing the material and replacing it looks like quite a job.

Thanks and sorry if there's an existing thread on this. I searched but I'm not quite sure what to use for keywords.

Search for "soundproofing". You'll find a hundred threads.

Pelican sells two different ones.... can be replaced. Much easier with the engine out, I hear.

That's part of the problem. There are a hundred threads and most aren't applicable.

Similarly, I can't even find a thread on changing the oil

No need to change the oil since these old cars just leak or burn about a quart/1000 miles. Just add when needed and voila!:D OK, not really...
The original soundproofing is bound to come unglued and disintegrate with age. As mentioned above there are a few replacement products to choose from.
You can call PP and ask about the ones they sell. They have excellent customer service and can give you some advice.

Just searched "firewall soundproofing", fourth thread from top:


http://forums.pelicanparts.com/porsche-911-technical-forum/190877-engine-soundproofing-replacement-how.html