A few questions
 

I'm thinking about purchasing vBulletin in the very near future and would like to ask a few questions.

I want to highly customize the design of the site preferably with CSS. Is any PHP required in order to build a custom template? Are there any guides for this type of modification? I also want to integrate Photopost as well. Is there anything special I would have to do other than customize the Photopost template as well?

If I do use my own template, will any of the modifications cause trouble? I'm mainly looking at an ad management program that allows me to place Google Ads next to text posts and allows members to view the site without ads after registering or for a certain time after registering. Which mod would be best for this type of advertisement?

Thanks

Well i believe to make a template you use CSS and html, yes for sure there are guides about anything, its in the archives forum tab at the top. I dont know what you mean about integrating photopost, but im sure the module can be made.

No not if its done right. And there are many modules on ad's just try them out or just see based on what the post information of the module gives you.

Then the upcoming vBulletin 4 will be very useful to you, as its design is based around semantic HTML, with CSS playing the largest role in styling.
No intimate knowledge PHP is required. Templates are HTML/CSS/JS only, with some variables and conditionals. The only "PHP knowledge" required is simple comparison-type expressions.
That really depends on what you're trying to achieve.
Photopost is a vBulletin modification, and uses vBulletin templates. By customising the vBulletin styling (e.g. replacing images, etc.), these changes will show on the Photopost templates as well. However, if you want to change the layout of how Photopost will show things (for example), then of course you will need to modify their templates.
You just need to make sure you retain all of the information you need on that template (e.g. variables).
This would simply require some template edits, and we can help you with that once you are licensed.

Thanks for all your help!

I was originally waiting for vBulletin 4 to come out but it seems like it will not be out for a while. I want to get most of the work done during the summer before school.

Replacing the tables with CSS should be no problem?

It's possible, but will take a lot of work to do this in the current vBulletin (3.8).

Possible to replace tables with CSS, yes, but I'd say wait until vBulletin 4 comes out with it's as mentioned above CSS layout/semantic style where you can make the changes you want via a few quick CSS changes rather than going into and modifying half the code.