First let me say, Welcome to AA!!!
Now explain what you mean by FW
Are these just regular rocks that have built up bacteria like a biowheel does, or is this some name brand product I haven't heard of yet?
If it's just regular rocks then you don't have to remove them.
Whatever is growing on them will die-off, help with your tank cycle, and end up being replaced with the nitrifying bacteria to make them SW
Make sure you add enough live rock to make a total of at least one and a half to two pounds of rock per gallon to give the bacteria enough surface area to filter your tank properly.
Like Hara said, if you buy live rock that's already been cured then your cycle will be quicker than if you use dry base rock, or uncured live rock.
Ask at your local fish store to see if they have fully cured live rock and how much they charge per pound. (about $6 - $8 per lb. is average around here with smaller pieces of broken rubble running around $4 a lb.)
In the end it's a little more work and a lot more $$$ than FW
, but the rewards are well worth it!
If you just take it slow, keep asking questions, and follow the advice of the veterans here, they'll guide you to a successful SW
experience... they certainly did for me.