looking to buy new sprockets and a chain for my 2006 f4i. plan on buying the parts now and then dropping it off at the shop for them to do. what should i buy

 

Depends on what you want it to do.

Quicker acceleration you could go down one in front or up two in rear or a combination.
Higher top speed up one in front or down in rear.
Or buy factory sizes and keep same acceleration/top end.
Then you can decide in chain 'size'. 520 or 525. I would stay with the 525, it will give you slightly longer service life but weight just a tad more which usually isn't a big deal if you're not using it for racing where every 10th counts.
Of course there is steel and aluminum - again weight vs. longevity.

If you're not racing/stunting I'd advise stock number of teeth 16 front/46 rear and a 525 o-ring chain. Buy a good name because you just never know where the eBay special was made (well, you probably do) and how long it will last.
Names: DID, RK Racing, JT Sprocket, Vortex.

Most of all, clean and lube it...

 

Drop it off at the shop and let them order it if your having them install it.

 

Just make sure you know what they're ordering. Don't let them charge you for a premium chain and then install a no name one. Also, inspect how well they riveted the master link. If it's split, make them do it again.