I assume bog = Bondo (filler) - Yes, I've replaced the sill's, matter of fact I'm in the middle of doing them both, got the right side done, you'll see in the pic's - time consuming but not too difficult to do right. If you want a f***ed up sill then shove beer cans in there, smear mud on it & think nothing of it, on the other hand if you want to actually replace the panel then heres one method...

sorry, cant seem to get the orientation right on the above pic - thats the rocker cut out w/22 Ga. steel strips welded behind the cut portion of the rocker/sill. the replacement metal I pounded into the proper curve & then spot welded it all in.
theres a little piece that went under the bottom of door that needed replacing too.



heres another of the sill patch & quarter panel patch welded in - thats coated w/POR-15 paint BTW...


theres a down & dirty way (beer cans & mud, gotta give em credit for creativity though) or an actual long term repair, certainly your choice. It's not that hard to do right, just takes some work & obviously more time.
Good luck!