Reddit mentions of Comprehensive Catalog and Encyclopedia of Morgan and Peace Dollars

On the grading part; there are three circumstances that I'd like something to be graded: to increase its value, to authenticate it or to keep it safe (for something sentimental). Unless a coin is worth 250+ I wouldn't have it graded, I'd just throw it in an air-tite and tube.

PS: I love Morgans, that is the majority of my collection... all the way from cull Morgans to MS-66. If you are serious into collecting silver dollars (Peace and Morgan) I recommend you spend $40 and purchase this book:

http://www.amazon.com/Comprehensive-Catalog-Encyclopedia-Morgan-Dollars/dp/0966016823

As others have said, it is perfectly fine to collect whatever you want. It is your collection, so collect whatever you find most interesting. I've known people that collect just Bust half dollars, or Indian cents, to almost the exclusion of everything else, so do what you like to do.

Other than maybe a few inexpensive coins to get started, I do suggest buying books. Hard to know what is out there, or if a price is reasonable, otherwise. For American coins in general, the Redbook is inexpensive, and covers many things. Over time, you may want to specialize enough that the Redbook isn't specific enough for what you want. For instance, if you collect Morgan or Peace dollars (you didn't mention what kind of dollar coins you are interested in), you'll want to pick up the VAM book. The last printing is a bit out of date now with new discoveries (the VAMworld site is more up-to-date), but it has lots of info that is still valuable. I like to collect all sorts of things, but, for example, do collect Morgans with interesting varieties so need books like that one. There are related books for other coin types, such as the extremely expensive Overton book for Bust half dollars, too.

As for buying coins, there are lots of sources - eBay, local coin stores, shows / coin group meetings with bourses, directly from other collectors via Reddit and such... At the start, I'd suggest buying coins in person, rather than via the Internet, though, so you can get a feeling of what a good, natural coin looks like - photographs can easily mask problems such as cleaning or artificial surfaces which would lower the value of the coin. If you can see a coin in hand, you can better judge if it really is for you.