I am 50 and dealing with my 2nd childhood...so please be kind to me...
My 16 year old son and I have torn down and rebuilt/replaced alot(to put it mildly).
We purchased new front inner and outer fenders. We have never primed or painted old or new metal on cars before so I'm in need of some advice. Do the new fenders have to be stripped or cleaned or sanded prior to a primer oris the black paint on them the primer and we just paint over this?

The black stuff or 'e-coat' is excellent. When I refinish a customers car that has new OEM sheet metal on it, I sand the e-coat with 320 grit or finer paper. Some people are satisfied with just a red scotch brite. Either way you are giving the paint a 'tooth' so it will stick. After the metal is prep'd, then you wash it and tape it up etc., etc.

One thing about e-coat, if its a Taiwan part, see if lacquer thinner will make it soft or feather some away. If the thinner takes it off or the feather edge is ragged, it would be in your best interest to take it all off. The USA made sheet metal usually has a nice e-coat on it.

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67 Camaro SS Conv.
70 Challenger R/T Conv.

Ragtopman is right about the Taiwan E-coat.
I assume you have the time to do this right or you wouldn't have a classic in the first place.
Sand the e-coat with 240 or finer sandpaper and if you remove the e-coat, use a self etching primer as a base coat. Let it dry per instructions and then spray two (2) coats of quality primer evenly over the parts. Let them dry (and shrink) for at least a day in a warm area before block sanding. Block sand the parts all in one direction using water as a lubricant. You can either squiggy off the residue or let it dry and wash them off. Let them dry again. Any dark areas are low spots and any metal showing is a high spot if you sanded it correctly (evenly). Spray another coat of primer and let that dry for a day in a warm area. Sand the entire part with 400 paper, evenly again and you're ready to apply the paint.

Use 320 wet or dry paper to block sand the primer.