I think Jeff pretty much covered it...
I certainly won't argue with his advice to buy my book! :dance: He's about right on materials cost...labor would run the price right on up there if you have to pay for it. However, installing a tank isn't rocket science...and I'll be glad to help you spec out the system and how to install it.
Depending on where you're planning to put the boat--and your budget--there MAY be a better option than a holding tank for liveaboard waste management: a CG certified Type I MSD (device that treats waste and discharges it overboard legally and is far more environmentally friendly than a tank. If you're gonna be on an inland lake, you're stuck using a tank, though.
If you'd like some help, email me (to do that, just click on my name above the photo to the left of this post and follow instructions)...I'll be glad to help you do it.