I posted a list of the pokeball throw sequences here: http://www.pokecommunity.com/showpost.php?p=4238206&postcount=1507
Look in the thread that I link to in my sig and there is a link to a zip file with some tools that will allow you to do this. (Its at the beginning of the basics section).
What you need to do is extract the narc containing the sequence for Riley and the palette for Riley as well as those two files. Do this with tahaxan tihaxa. Then use PPNFR (also included in the zip) to insert the palette and then the sequence for riley into the place where the palette and the sequence for the hero is (respectively).
For the back sprite and the front sprite use loadingNOW's PokeDSPic, get it at http://pokeguide.filb.de/, to find the values for the image in \poketool\trgra\trbgra.narc and \poketool\trgra\trfgra.narc. You can extract the riley ones and insert them into the spot where the hero's are with PokeDSPic or use Tahaxan tihaxa and PPNFR as well.
There is a list of offsets for the overworld sprites for DP here: http://www.pokecommunity.com/showpost.php?p=4236332&postcount=1504
take the ones for DP and make a file named list.txt and put it in a directory with PokeTex. Then open your DP rom in PokeTex and find the overworld sprites for the hero and Riley. Use tahaxan tihaxa, look in \data\mmodel\ and find the files that would inclode those offsets. Extract the one for riley and insert it with PPNFR into the spot for the hero.
This is a really way job if you know what you are doing. Try to do it and if you have questions let me know.
If by any change you don't know what extracting narc files or files inside narc files means, read about it in the thread I link to in my sig.
NOTE: This will not edit the overworld sprites for the hero using surf or fishing, etc. For that you would have to edit that manually using PokeTex. You can find an Poketex that is in english (for the most part IIRC) in the Diamond & Pearl & Platinum Hacking thread. Use the search function to search there.