Magento Theme Customisation

Hi, I am currently developing a new e-commerce website for a client and the solution that I usually use (OpenCart) does not have the sophistication that I need. I have never used Magento but the admin interface looks similar to OpenCart. I understand that Magento offers much in regard to the general functionality.

I want to produce something similar in relation to:-

1. Drop down navigation
2. The position of the information tabs (right of product photo)
3. The way that colour options are shown (my clients products have up to 40 options)!

I will be able to provide you with comprehensive visuals of what the final design should look like. I only need the general template (theme) working correctly, other than a couple of test products - there are no products to enter, I will look after this myself.

Any questions, please do not hesitate to contact me.