You will probably learn quickly, if you don't already know, that restoration usually boils down to individual choice, and you'll get both sides providing reasons for why you should, or should not, do restoration. I agree the small items, lid and rear pipe, are a no-brainer to replace/restore, since they both detract significantly from the rifle's appearance. When barrel stretching enters the conversation, it's really up to you on how you want your rifle, and your investment, to look.
At times when a gun has had other restoration done to it, it becomes viewed as a "restored gun" in the collecting community. The value is dinged somewhat, so it partially becomes a financial issue: if you want to invest a good chunk more in a proper barrel stretching and forestock addition... will you get your full investment back out of the rifle? Probably not on a mid-range gun, particularly if it has other restoration that can be picked up by a good collector. So the real question is how you feel about your gun as it presently looks.
Since this is a personal decision, I'll offer a consideration I use for barrel stretching. Consider how the rifle looks presently; does it look snubbed off and awkward to you, or does it look "reasonable" even with a few inches missing on the barrel? If a rifle looks clubby or awkward, it probably will look that way to a future buyer, too, so it may be worth your investment to stretch the barrel, for both your satisfaction while you own it [which is a key part of its value to you] as well as for an easier sell down the road. If the gun looks reasonably OK to you with a few inches of barrel missing, it probably will look that way to future buyers, and it's probably a better decision to leave it as-is.
Shelby Gallien