First of all, do it. Don't second guess yourself, just open up an account. You can put 25% of your compensation or $45k (whichever is less) into your account. It is one of the best deductions available for the self employed.
You can set up a SEP-IRA at just about any broker. Mine is setup with BofA and the entire process including funding was done online electronically.
The only real decision is how you are going to invest your funds. But setting one up is a no-brainer.
Just do it.