Not exactly sure what to tell you on dropping the front sump to fill or not. If they recommend it, I'd say just do it.
I do want to thank you for sharing your project with us, and all the great pictures as well. Best of luck, and please do let us know how it all ends.
I'm not wanting to hijack your thread, but if you take your time, you can do anything. I'm proof, I did a 5hp24 rebuild all by myself a while back and that sucker is still running 3 years later: http://www.bimmernut.com/forum/5-ser...tml#post328268
I've actually been very proud of that rebuild, I thought it was quite an accomplishment. I know by the looks of what you been doing, your's will be successful also.