I will address part of this and if you have decent internet you should probably watch this video, you will find it much easier to watch the steps involved rather than me trying to explain them. The build is done using the Sony S600 camera, probably my favorite because of the brightest flash and awesome picture detail.
Charles Garrett is a great friend of mine and is probably the person most responsible for getting me and thousands of others into the homebrew trail camera hobby. I don't expect the link to work so copy and paste to your favorite search engine, Google, etc.
Look for How to build a trailcamera about 3/4 way down the page, specifically one using a Critter Getter control board.
http://www.diytrailcams.com/
Cost will vary depending upon the camera used, the above build was done using the S600 camera shown in the video.
DSC-S600 camera...ebay and depending on what's available and how patient you are.
$45.00-$60.00 average.
Charles will modify your camera for use (he does all of mine due to rheumatoid arthritis)
$15.00 plus shipping both ways...average $26.00
A waterproof case is a must have....average $20-$30.00
CritterGetter micro control board from Firemanjim and set up for use with the S600 camera.
$48.00 avg. including shipping
High Performance Wide Angle fresnel. $6.00 plus shipping, .
Glass required, pipethru tube for security, Marine Goop, . approx. $18.00
Did not figure in but will be needed, you decide.
Soldering iron and solder must be figured into cost, must be capable of doing fine, detail work.
So........I figure an average of $150.00 for most builds although some savings can be recognized in shipping costs at times by buying in multiple items sent at the same time.
Cameras are generally purchased used on ebay and carry no warranty but that is a mute point as a brand new camera modified for use would void the warranty, garage sales and friends/relatives are sometimes a great source as well. I find the cameras to be quite reliable as a rule, I have some that are 10 years old and still functioning perfectly, I have also had cameras that lasted only a year or two so it's a crapshoot.
If a camera fails you don't throw away the build, you just put in another camera.
Control boards are all in all very reliable and come with a 90 day warranty as a rule. Unless one is careless and lets moisture get in the case (checking cards in the rain, or flooded conditions, etc) they seldom are a problem and of no real concern. If a board fails you don't throw away the build, you just replace the board.
90% of my builds come with a tube installed and yours should too if you have any concerns about theft.
A Masterlock Python cable of the appropriate outside dimension can then be threaded thru the tube preventing it from being simply opened and tampered with but as we all know there are unfortunately thieves out there who will find a way to destroy or steal it, it's the world we live in today.
Firemanjim also builds and sells homebrew trail camera for those who might want to contact him. Again the link probably won't work so copy and paste. For me it's a hobby to occupy some free time between seasons, for him it's a side business and I know he would like you to visit his website.
http://www.jtswildlifecameras.com/