Modifying store pages and display

All –

I am finally getting back to working on my site, and am seeking advice on customizing the actual display of listings, as well as how listings are entered

I was hoping someone might be able to confirm the below is possible, and possibly point me to which page to modify (should this be done in a child theme?)

– When a user adds a listing, I would like to pull their company name with the form they are completing. This should be possible by modifying the listing page, but I am not sure where to put the code
– When a visitor clicks on a link, I would like be able to also add logos to the listings displayed.