Where to hire a Discourse guru?

I am sure that if you search :arrow_upper_right: you will find the answers to your questions on your own. What you are asking for is really basic (even if you do not know CSS at all) so if you lose a bit of time you will find the related topics.

For example, for the rounded buttons there is the component Discourse Button Styles.
You can also take a look to Material Design Stock Theme

For large font just add this in your stylesheet (16px as example, you can change it)

    html {
        font-size: 16px !important;

For uppercase use the property “uppercase” on the element (p in the example below) you want to transform

        text-transform: uppercase;

You will find many topics that talk about these changes, use the search!

I do not want to take Jay out of work, but these changes are really really easy