I am not 100% sure this is what you are looking for but will give it a stab since it is week-end and may be Monday before you get answer.
If you are trying to change your listing from one font to another you will go to the listing grey area under item description. Go across top row a little over 1/2 way over 2 things past the bincoulars, and you will see what looks like a little square patch or picture frame it is blue greenish with little black things around it when you hover over it it wills say SELECT ALL. Click that and it will select entire listing making listing blue. Then there is little eraser next to that looks like chalkboard eraser. You click that and it will make your entire listing to small with no html in it. (it does not erase the text, just the html) After doing that listing is still highlighted in blue and you can do entire listing on whatever font you want and size. If you are using assorted sizes, you will need to highlight what you want of each size and it should work.
***To do the first one I would do create new from an old listing and try it from that one so you do not mess up one you love. (or if you think you messed up original you could back out of it without making changes at all). I usually just do create and then when I am happy delete the old one, especially on first try.
I think. . ??? this is what you are asking if not I am sorry if I wasted your time.