You are correct that it's appropriate to visually distinguish when you're mentioning a word as a word instead of using it for its meaning. This is called the use-mention distinction.
Quotation marks or italics are appropriate for making the distinction. If you're using a style guide, look for “use-mention distinction” or “words as words” to see what it recommends. The style guide will also explain what kind of quotation marks to use and where to put the commas.
If you're not working with a style guide, there are general guidelines you can follow. The main concern is placement of trailing commas and periods. There are two common approaches, often called typesetters' style and logical style.
Typesetters usually italicize trailing commas and periods for aesthetic reasons:
In the text, words such as greenbacks, ironclads, and blockade were used.
Traditionally, they also put trailing commas and periods inside of quotation marks because of the mechanics of movable type. Most (but not all) writing in the US still follows this tradition:
In the text, words such as “greenbacks,” “ironclads,” and “blockade” were used.
Elsewhere, quotations usually follow a logical rule instead, putting commas and periods outside the quotation marks unless they're part of the quotation:
In the text, words such as “greenbacks”, “ironclads”, and “blockade” were used.
Also, as an Oxford Dictionaries article notes, British English usually uses single quotation marks:
In the text, words such as ‘greenbacks’, ‘ironclads’, and ‘blockade’ were used.
As for greenbacks: It's not a proper noun, so only capitalize it where you'd capitalize a common noun, like the beginning of a sentence.