Door framing in load-bearing wall

I would appreciate a quick run-down on the proper way to frame a door in an existing load-bearing wall. I do plan to get a permit and have the work inspected, but I'd like to get a handle on the right way to go about it.
The wall:
I've verified it's a load-bearing wall by looking in the attic; it runs perpendicular to the roof trusses. There are no floors above, so the only load is the roof itself. The next nearest opening from where I want to put the wall is just over four feet - that is to say, once the new door is in, there will be 48 inches of wall between the new doorway and a currently existing-one. There will be no other openings to the end of the wall (and the house), about six feet going the other way. The doorway will be for a 30-in. wide interior door. Here's a (horrible ASCII art) drawing, very roughly:
Existing New 30-in door |<-- 48-in -->| door |<-- 72 in. (approx) -->| ----------[===============]**********[=======================|| || || ||++[]++++[]++++[]++++[]++++[]++++[]++|| || Temporary support || || || Non-load-bearing -> || House end wall -> ||
The non-load-bearing wall above will be about 5 in. or so from where I want the new door to go in, which I don't *think* will be a problem. I've also verified there is no electrical or plumbing that needs to be moved.
I've done some looking around online and as near as I can figure, I'll need a header across the opening made of 2 2x10 on edge with plywood between to the width of the framing, supported on cripples placed to the width of opening I require. What I'm not sure about is how far past the width of the new opening they have to extend? I would assume they extend as far as the next uninterrupted stud on each side, but you what they say about 'assume' - makes an ass of u and me :-D
The related question is how I support the load while doing the work; my current thought is to put up a couple of 2x6 on edge, nailed/screwed together, against the ceiling, running from the non-load-bearing wall to the end wall and supported with 2x4s spaced 16 inches apart, or jack posts, all resting on a 2x4 flat on the floor. Not sure if the bottom 2x4 is needed, but this work is on the 3rd floor of my house, so the load had to be transmitted down somehow, and doing it this way it seems to me I won't need to be quite as concerned about putting the temporary verticals right over the floor beams. I'm also thinking I'll need to take the drywall off the ceiling where I put the temporary 2x6 support, as I can't see drywall taking compression loads too well. Or is that not a concern?
Anyway, my great appreciation to one and all for any help you can provide.
Yours aye, W. Underhill
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William Underhill wrote:

That doesn't necessarily mean it is load bearing. One advantage of using trusses is that THEY carry the weight and walls are not needed; desired walls need not be load bearing. I have numerous interior walls perpendicular to the trusses and only one is load bearing because it is at the juncture of two wings.
That doesn't mean you shouldn't do your framing in a standard manner.
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dadiOH wrote:

Hm - good point. My background is marine electrical, not domestic structural, so definitely a layman in terms of the finer points of framing. Thanks.
W. Underhill
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Normally you need the rough opening to be about 2" wider than the door. In addition to the cripple studs that will support the header you should put full height studs next to them for added stability and a place to nail the molding. Google "rough opening framing" here is a decent picture for windows but the idea is the same for doors:
http://www.hammerzone.com/archives/window/new/ro_framing.htm
As far as the temporary support you *probably* don't need any. You will be taking out two or three studs so you should be fine. If you want to support it here is what I did for a much wider opening when I was worried about it.
Cut out the drywall. Screw a 2x8 that is much longer than your opening to the top plate of the wall up against the ceiling. Wedge some 2x4s under the 2x8. Install your header. Take out the temp support.
Good luck.
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RayV wrote:

...
Very helpful link, and excellent diagrams! Thanks!

Thanks for the suggestion; much less work than what I had in mind.
Yours aye, W. Underhill
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