How many guide sets are there?
Every router has it's own guide set.
Now, the best are brass. They finger tighten, won't work loose and won't damage router bits should something go amuck. Steel ones may grab the bit and create a projectile of themselves and/or pieces of the bit.
Does every manufacturer have their own?
Yes, pretty much. There are only so many sizes that can fit the space but everyone has a slightly different attachment method.
Is there a certain select few that fit all brands of routers if you know which ones to use? Are there differant installation methods (my Bosch has a spring loaded lever that you push to insert the guide)?
I was hopeing to find a good web site that explains in detail for us people who have never used a guide before and have only just purchased their first quality router.
There will be a series of essays available on this and other topics in the new FAQ when it is assembled.
You want to take a look at Oak-Park.com. Here's the rub: you take off the baseplate of your router and replace it with an OakPark one specifically for your router. Use the 7" for hand held template operations. Then, you have a wide assortment of guide bushings available from oakPark and LeeValley. All are brass screw on and available in a professional range of sizes from very small to very large. You can use the same guide bushings for the 11" Oak Park table insert. Baseplates are available for most routers and if there isn't one, it's not difficult to make one.
Sorry if I'm asking stuff that sounds routine to you, but it new tech to me.
Ask away. No such thing as a dumb question, only dumb answers. If you ask there are dozens afraid to. That way, they get the info too.