Wow, you have a nice looking teardrop there. I wouldn't be too concerned about making changes in order to make it more comfortable. Unless it is a vintage, one-of-a-kind, much desired, original teardrop trailer, I wouldn't hesitate to alter it to suit your special needs. I think that insulation and sound-proofing, might not be required, especially here in our temperate climate, in California. I guess if you plan to camp in the high mountains, it might be a different problem.
So get to cracking, go ahead and remodel it, to what ever makes it more camp-worthy. After all, you are the one that will enjoy it in the long run. Twenty years from now, no one will care what changes you have made, since it was done to suit your particular needs.
As an aside, I suggest that you make plans to attend the once-in-a-lifetime, 18th Dam Gathering at Lake Shasta, April 28th to the 30th. This is one great teardrop gathering, that you just don't want to miss. (You're welcome, Grant)......who has been promoting this event for 18 years! If you fail to attend this wonderful gathering, shame on you, look what you have missed, sharing your teardrop find, with other like-minded TD' ers.
So bottom line is, we hope to see you there, with all of the other various shapes and designs of teardrop trailers, most of them, clad in aluminum, woody, fibergalss or Line-X coverings. (Lets see, what else, wood-strips, canvas, sheetmetal, Lowes 1/4 inch plywood, stainless steel (not hardly) and soon to come, space-age, carbon fiber constructiion.
Some may have other exterior finishes, but many of us, lacking common sense, are simply showing up with wooden, TD wonders, and often when or if it rains, turn into cornflakes, if the weather turns for the worst..... (I know, I've been there!, Ala, Dam Gathering #10!)
So, plan on attending, and go with the flow. No one expects perfect restorations, one-of-a-kind individual designs, or any kind of "violations of original builds, (which many of us know little of) or what ever floats your boat.

Roly, hoping to see you there, and plan to enjoy some Prime-Rib dutch-oven marvels.