Construction Question

Rectangular room, coffer'd ceiling, tiered platform seating, Russ Herschelmann's proposed seating and speaker location plan (See old "Home Theater Architect" articles on seating and speaker placement, as well as acoustic treatment), some processor with newer Audyssey DSP room correction tech and multi-channel amplification, PMI "Cine-pannels" around the room, A Klipsch THX speaker system (for passive speakers, you'll not get better for movie playback - within reason), comfortable medium-backed seating, -and you're done.

Er, you might wanna add a projection system and high def sources. My bad...

Just know, that's there's so much to know! In terms of "performance" aspect of the theater - in regards to construction, room acoustics, sound-isolation, noise control HVAC system design (noise and ventilation factors) system power distribution, layout, speaker/seating placements within the space, style of seating, equipment selection, cabling, equipment isolation (can degrade system performance if not done right), just to name a few! Just know, that if you're doing everything yourself in terms of the selection and design process, that you're going to be compounding shorfalls likely! Many of us have been in and around, as well as doing this stuff for decades - AND WE'RE STILL LEARNING SOMETHING NEW ALL THE TIME!!! Therefore, just don't expect to "hit it out of the part" on all the issues and choices you'll make, going the DIY route! That's the way it is.
However, if the joy of going that route is the ultimate pleasure project for you, that's another story. Just know that you won't know how it ALL fits together like a professional with a proven track record, if you forgo getting professional assistance.
Seen it hundreds of times over the years. These are constants really.
Infact, I would EVERY TIME recommend to someone who had a reasonable budget- and was going to DIY as a novice/enthusiest - that they even consider downgrading their equipment selection potential choice, and spend the rest of professional help! The end result will most always yield you far better results than if you spend the money on the gear, and don't get some consulting and help. FYI
Choices...

In fact, not only have I fixed nightmare systems that so-called "seasoned expert installers/integrators" have designed and installed, but I've been to homes of enthusiests who've built dedicated custom theater spaces from scratch (like your doing), who actually ended up having their theater rooms displayed in major magazine publications! - only to asses all the major flaws, short-comings, serious issues, and bad choices they made, and knowing how they could have done several hundred percent better on the results, in literally dozens of areas!!!
So, I'm not trying to rain on the party. Infact, I encourage and applaud the effort! I personally however, like above-par, stellar, even world class results from custom theater ambitions. And I know what it takes to achieve that...years and years of knowledge, experience, and trial and error.
good luck

Ralphnoonan, you have to forgive us for out zeal in trying to help you put together a truly quality home theater project!
We here at A'gon (and I think I speak for many here), simply are interested in not only ourselves, but people like you who are DIY'ers (if Novices) getting excellent results from your project. Many of us know that, without some expert guidance, your system will go the route of the vast majority - mediocre-ville! And we simply don't want that for you, in our selfishness. So for that, please for give us.
Back to your question:

"Does anyone know where a person could get some info or plans on the net?"

Yes, simply go to www.google.com, type in "home theater construction techniques, and pull up a near endless supply or information pertaining to your topic!!!
You will then have about as much varying opinions, suggestions, bias's, differing design ideas, construction techniques, varying views on room dimension recommendations, structural design parameters, and as many opposing view points, as you will get by asking everyone here on this site, which equipment you should chose!!!
Sorry, but I simply don't see how getting someone to point some site where you might find "one person's" recommended building plans for your job, where you can actually decipher whether they would be what you would want to chose for your project!!!
But, that's just me...
Good luck