flathead jack
 

2002 7,3 can diesel fuel get into coolant if so how

yes, and I believe I have read that it happens when you have bad injector cups.

flathead jack
 

wonder what this will cost

wouldn't be too bad a job to do yourself with the cup tool. You can pull them without removing the head fairly simple with it. Have you ever pulled injectors?

no new to psd

its not hard there are step by step instructions on line just serch for how to pull injectors on a 7.3 i have done it several times just make sure to drain the oil gallery

It's probably injector cups...

Not definitely, although I can't really think of a more likely way for fuel to mix with coolant. Any white smoke at idle?

It requires a special tool to remove cups, but it's not supposed to be that hard to do.