It would seem that the easiest path is to take over the party.
It really would not be that hard. Look at how McCain surged after he picked Gov. Palin and how he fell and never regained his lead after the economic bailout. The point being a huge majority in the GOP are conservative Christians who do not want govt in all parts of our lives.
In order to regain control PACs are going to have to be formed that the majority of our contributions go to. If the GOP doesn't return to our beliefs they don't get our money (think moveon.org).
Conservatives don't have their equivalent of George Soros. 99% of conservatives are simply hard working middle class people who live more or less pay check to pay check and who dream of someday being able to retire in comfort.
The Republican party has long been run by North Eastern liberals who live off contributions from billionaires and corporations. That is why the Republican party is often referred to as the "Party of the Rich".
I'm not sure they would miss our $100 donations. Also, I don't know how a conservative is supposed to work his way into the RNC heirarchy. In fact, I don't even know who runs the Republican party.
BTW what do you mean "regain"?
It is underway right now.