Is this font/font style change easy? Hard to explain

I just want to ask if this is something that can be changed easily. I’m looking at purchasing a theme and I’m torn between 2 of them. The one I’d prefer has a look to the text that bothers me.

Here’s the style I don’t like:
https://oi39.tinypic.com/23sh2q.jpg
As you see it’s so skinny and the font is different and it’s just hard to read.

Here’s the style I like, what I would consider normal on a website:
https://oi41.tinypic.com/lkzsz.jpg

Is achieving the second an easy task? Will it cause problems in the theme?