My guy is pistol armed, vastly out numbered by rifle armed peasants, and needing to carry his unconscious friend out. This smells of stealth but I haven't been able to find a path where I'm not seen and killed on one or two shots. Is there a stealth path or do I have to kill everyone?

If you're talking about the mission "Into the Lion´s Den", where you have to get into the Marshal's hacienda, then no, there's no stealth way in and you aren't allowed to kill the guards either. You've to knock them out, mostly by using a Kate-Sam-Cooper combo. Use Kate to lure a guard into a kick :-) let Sam tie him up and Cooper drag him away.

I don't think we're talking about the same hacienda. Getting in is easy - just talk to the owner and tell him his hand owes you some money. Its getting out that I've been floundering at. My friend was knocked out for stirring up trouble with the other hands and I have to get him out while the owner's fiance distracts the guards. This is a very early mission with the first character.

There are no longer any videos or walk throughs for this game on the site linked here.

But there are several alternatives on YouTube by now:
https://www.youtube.com/results?search_query=desperados+southern+comfort

Haven't watched them, but I'm sure one or two give a good picture on how to solve it.

It is true, the game has a textual defect. The briefing says go South to the barn behind the farm; it should say: go South to the stables ahead of the main house, or something similar. What is interesting is that the main scene happens in the one and only barn in the scenery, the start of the adventure, not the final goal, but you do have to go South from the starting point once you recover control. I needed two or three runs to realize stealth would not work and shooting was suicidal, but tot find out about the stables I had to experiment waiting for triggers around the barn and go to the video to see the solution.

I so very much like this last post that I had to reply, even if 2 years old.
This is very true. Barn to me is the one that has hay tied up in the air. And my English was plenty good back then, even if I was born in 1985 and I am not a native English speaker. This bugged me more so in 2001, 17 years as it turns out is not that long, so I knew what to do now in my second play through.
Back then I probably moved around the barn as crazy, then decided to kill everyone, and then needed a couple of minutes to get to the right position to trigger the scene.

Then you have mission 9. It mentions valley, valley to me was 17 years ago and is now the one that has a road leading to the north. It's what most people think of when they hear valley, narrow and surrounded by rocks. It probably confused me the most that in every mission before you had to escape on a road.
What's more interesting, what I thought is a valley is actually a gorge, which is mentioned in mission 11.
And then also the thing with the horses, I needed 50 minutes to remember playing it 17 years ago, that you also need to take the 3 horses without saddles. And then when I knew you don't have to escape with horses, I figured out for next time that even one saddle is enough to take all the horses to the valley, it just takes more trips.

Then there's mission 11, it says you have to kill everyone, then it says you can also blow up the boulders.
You have to blow up the boulders in any case, even if you kill everyone.
As it is written, one would presume that they would finish the mission if they kill everyone or if they blow up the boulders, but you can finish it only if you do the second or if you do both.
It's no problem to figure out how to finish the mission, it's just that some players would try to kill everyone even if they don't actually have to.

Here are all the not absolutely clear briefings word by word:
2nd: "You have to reach the barn to the south behind the farm with Sam"

9th: "Sneak through the woods till you reach the paddock; take the horses and head north west to the small well-hidden valley!"
I feel stupid now, as it clearly says north west, and even points a camera to it during briefing, so that's on me. John also says at the start that you have to steal their horses except the leader's horse. So that means all the horses in the paddock.
Briefing is also strange, as there is only one prisoner:
"And we need to get rid of the prisoners once we've stolen the horses!
You reckon the soldier will cooperate?
He won't have much choice - I'll free him, knock him out and drag him straight off.

11th: "Take out all the opponents lying in wait for you in this gorge to be able to cross the canyon safely!
You can also blow up the piles of boulders at the other end of the gorge to ride through and go further north!"