Is it hard? Do I have to add a lot of extra stuff?
In nearly every case, no. The amount of work needed is minimal compared to the effort it usually takes to make a page
Once you know what you're doing, it's usually quite easy to make a page that can be used by everyone.
Designing for Universal Accessibility
A FedWeb '98 Tutorial
Presented by Kynn Bartlett,
President, HTML Writers Guild