I had a go at converting a loco to DCC last night. In this case, I started small converting my model of 45 114 following the pretty straightforward explanation (with pictures - I like pictures!) found here Farish Diesel DCC Fitting. I had to remove quite a chunk of the metal from the end with the chip and socket (I decided to put the socket in so I can put a blanking plug in to run on DC - it also meant if I did any dodgy soldering, I wouldn't be damaging a chip) and it still isn't fitting quite right so I will probably have to unsolder it all, pull the whole loco apart and remove some more metal. The blog which I followed suggested a milling machine would be best but I found using a file just as good - if a bit time consuming. The best part was, having put it all together it worked - and has been programmed using my NCE ProCab. So now to the next - a Class 33. The grand plan is to do all the blue diesels in DCC and having done this one, it should be a doddle - although I will have to work up to the 03, 04, 08 and 14 I think.
EDIT - a couple of hours later and I have removed some more of the metal under the chip and it all fits perfectly. I had to sacrifice the cab moulding at that end, but I am thinking of detailing the buffer beam at the other end in any case so the end with the cab in it will be leading. It isn't noticeable unless you look, but knowing it is missing, I will see it every time that end leads if I don't make it a one way loco. Not sure what train it will get - possibly a Freightliner container set when I get around to sorting the collection I got on eBay a couple of months back.