Yes, most of the everyday look and feel of your portal is yours to change from your own admin login, with no designer needed. That normally covers your logo, your main colours, the banner pictures on the homepage, the headline wording, your contact details, your footer text and your social media links. You save the change and it appears on the live site, so you can refresh a seasonal banner or swap a logo yourself in a few minutes.
Where it gets more limited is the structure of the pages. The search form, the results list and the booking steps are built to work with whatever your flight and hotel suppliers send back, so those pages follow a set layout rather than being moved around freely. Adding a new page, rearranging the homepage into a different shape or changing fonts beyond the set we offer is design work rather than a setting, and whether that is included or quoted separately depends on your plan.
Two practical things to watch. Pictures look best when they match the size the banner expects, otherwise they stretch or crop in odd ways, so it is worth preparing images to the stated size before you upload. And always open the site on a phone after you change anything, because a banner that reads well on a laptop can hide your headline on a small screen.
When you have a moment on a quiet day, log in and look for the branding or appearance section, try one small change such as the homepage banner, and ask us in writing which parts of your plan are self-service before you promise anyone a full redesign.