Changing themes. Is it straight forward?

Hi there,
I am currently running i-Craft theme on my e-commerce website. Unfortunately, my logo appears really small and looks ridiculous.
I have had a quote from a developer to change the coding etc on it so the logo can be larger but it was a hideous amount. I am wondering if I change my theme to one that will allow a larger logo, is this going to be a headache and heaps of work? I am not a web developer or any kind of IT guru. Just a person handling my own website. I don’t mind if it will take a few hours but if it is complicated and I mess my website up I will kick myself ??
Cheers!