What do you mean by installation? Could range from setting the basic equipment up, to a complete room remodel with in-wall hidden system.

I don't like to send people away, but avsforum.com is geared more towards your question, and is a pretty good one. btw- I do my own installations, but I sometimes browse the custom installers lounge at remotecentral for entertainment  :)

As to spending a lot of money on speakers for an AV (TV) system, that's up to you. I would, but I always go for the best audio I can afford, even for television or movies.

How much room to you have around the TV?  Unless it is a dedicated room, space is generally a limitiation.  Do you have room to the sides of the TV?  Is the TV on a stand that can also store equipment?

Additionally, how many video sources do you have to accomodate?  DirectTV/cable box, Bluray player, etc.

In general, equipment and room specifics.

I want to tell you, first of all, that the vast majority of Home Theater receivers are absolute garbage.

The guy who goes out and buys one and thinks he is going to get 5 robust good-sounding amplifier channels for $400 or $600 is simply completely ignorant of the facts of life. For that price you get a power supply that can't adequately power most speakers, and that is why they don't sound good at all unless the volume is kept pretty low.

You can't build it and sell it for that price. Hell, a good 2-channel amplifier is hard to find for $1000. 

You can get the Cambridge Audio 551R for $1200, or the Denon 3312 for around $900. They are pretty good. There's not much else for under $1500 that i would recommend to anyone.

If you have the money, what I would recommend is that you get the Cambridge Audio 651R, which costs $2000 and is a tremendous value at that price, and then spend about $3000 to $4000 on a high-quality set of speakers. That can get you a very fine system for around $6000.

A multichannel "preamp" is called a Home Theater Processor, and they run from $2000 to $9000. A good 5-channel power amplifier will run several thousand dollars.Building a system that way, from separates, with a set of top-quality speakers, will cost you around $25,000 or so.

Anyone can hook up 5 speakers to a receiver, but you have to know which ones are the best value at a given price point. Home Theater Magazine has a guide for beginners that would be invaluable to you. Check out their website. Better yet, get a subscription to Home Theater Magazine immediately and you will learn a lot in a hurry.

If you state your budget for the 5 speakers, I could make some suggestions.

Paying a professional to do a whole system, including labor, will probably get you a batch of equipment that has a high profit margin for HIM and is not really very good for YOU, plus a lot of cost for his time and profit. Going into something like this in ignorance and putting your trust in someone who is in a position to screw you royally is a big mistake IMO.

Either that, or IF you get someone who can and will actually put in a GOOD system, he will charge you $30,000 or so for something you could easily do yourself for well under $10,000.

If you have lots of money to waste and want someone to hold your hand...it's your money to waste. Educating yourself a bit and buying your own gear will save you at least $5000, or maybe twice as much. You will also probably end up with a better system and be more satisfied in the long run.

So I guess you should contact someone like these guys, http://www.madronadigital.com/  Audio Visual System integrators. designers, installers, equipment sales all under one roof.

This is an example, you should contact someone like this in your own area. Just google Av system integrators in your area, or use yelp. They can do it all, and all you have to do is pay.

"figuring out how many people/companies it will take to do this" - it may not be as complicated as you think.  First of all, any dealer selling good equipment tends to be/have an installer these days too.  And connecting and setting up stuff is not terribly complicated.  If you haven't done any of that before, then I appreciate it may seem dense or difficult.  And if that's the case, then a dealer should be very helpful for you.

On the other hand, if you are looking for more of a built-in/custom/"lifestyle" setup, with equipment hidden in closets, speakers hidden in ceilings, that sort of thing, then you do need at least a capable general contractor to do some design and do your carpentry.  Again, the electrical connections aren't too taxing, you just need to do it right, so get help if you need that (from a dealer or a handy stereo dude or a/v friend).

Also, even if your audio guy doesn't seem to hugely specialized in tv's, no worries, he can handle tv hookups too. 

And here's an extra opinion:  The sound quality will be more valuable/important in your life than the video quality.  So get any damn HD set, but go for quality in your main speakers, etc.