Hi Tom,
I am a bit of a newbie myself! But maybe I can help a little.
From what you have described, I presume you have it written down or a picture of what you want it to look like, etc. Have you gone into the Host settings, and added in all the modules you want? Like the Events module (calendar)?
For the Gallery module - I purchased one that worked well called Lightbox Gallery - you will find it under the market place. (you can see it in action here: www.zoecakesforfun.co.za - and it appears in several places on the site). I had a slight glitch when I installed it and wrote to them, within moments tey had done an upgrade for me to reinstall, their attention and service was exemplary. I tried MyDNNspace first, but couldn't get any help or response from them, gave up after a few days and many e-mails. DNN have their new galery module out now I believe, but I have not looked at it or tried it. Maybe you could scout around and read what the others are saying. You may prefer to try it.
The replacing of the stockphoto - you need to have an identical sized photo and name it the same (as the stock photo), then upload it to overwrite the stock photo. It will be under portals, no time for me to give you the whole path now.
The logo is replaceable under Admin/Site Settings/Appearance ... it says Logo: and there is where you choose the File location, give it a minute if you changed it, and then underneath you can choose the file OR upload a new file from your own PC. Don't forget to update!
When you are in the main home page, click Add in the top control panel (above the header of your site). The page you are going to add will be no. 1 sibling, and the idea is to do it completely and with all the 'modules' you want on that page. Then you will save it as a template, so you can use it for the others. Pay attention to the Permissions, and the Parent Page. If you leave the parent page as ,None Specified> then it will become its own page, and make a menu item on the home page.
I cannot type more now as I have a meeting to go to, and I hope this gives you a starting direction.
Good luck and contact me if you want, look for my site called coachlorilea.com, you will find my contact details there.
Lori