Forgive me for not knowing the correct terms.

I am looking for life expectancy on the following items AND do these items need preventative maintenance AND who would I call to do the service AND what are the typical costs associated with PM of them.

~ Boiler (Also, should there be some sort of tray under it? It's just sitting on the concrete)

~ The HVAC unit that is outside the house (Big square unit with a big fan blade on top)

~ HVAC unit in the house that is in the closet that fires up when the heat turns on

~ Garage door openers

~ Cleaning of the dryer duct

Thanks for the help !

Pictures would help, but I seem to recall in another thread you had some shitty filter in your furnace is it stil the same one Dave's furnace? It shouldn't be a problem to have it on the concrete floor.
You should check the hvac unit in the closet for a filter and change it at least seasonally, more if you have allergies and many pets. Get a good filter 3M makes some good ones a MERV value of 10 or higher is good. The number is usually written on the side.
HVAC unit outside (aka condensing unit), as long as it's working leave it, check to see if the fins aren't clogged, pollen and leaves can clog it causing a reduced efficiency/capacity, clean it with by running a garden hose thru it and maybe rubbing LIGHTLY with a brush to not damage or bend the fins.
Garage door opener: lubricate, make sure there is no car under it in case you drop lube, I use motorcycle chain lube, only do this if it's a chain model not a belt model.
Dryer duct: clean out with a vacuum cleaner, and if you're up to it take the back off the dryer (make sure it's unplugged first) and clean out what is visible.
While you're at it do mine too.

All can be done yourself, if something doesn't work then call a technician, well call me first and if I can help you over the phone I'll only charge $50 per minute and for an additional 37 cents I'll talk dirty.