Hey, I realise this guide is quite old. I've just got the download content and this has helped a lot. Few things I'm going to add for those who haven't done this yet.
You must go to select event to choose to join with the Date force after a few battles. I think it costs 50 orbs, I done this around an hour ago and wasn't really paying attention.
Accept anything which has "Cost 0" You're usually given free orbs or gold or some random crap. Getting orbs is alright though.
If you think level 100 might be daunting, it's not too bad. It's different from the normal missions. All doors are open and the only thing you have to do is kill the main commanders on the opposing team. So it takes around 2 - 3 minutes per mission as you don't need to pay attention to anything else. If you have the original 1000, then you should have a pretty strong character. I'm using Yukimura Sanada and it hasn't been a challenge at all. (Probably because I have him at level 70)
To get the "Escort the princess part 2" mission. You must purchase the "Rescue the princess" From the select event option. I think it costs 20 orbs. Then there's the "Escort the princess" Which I think is 15. Definitely not more than that for either mission but I don't remember precisely. Self explanitory really but for those wonderng why they can't find certain missions then this will help you.
I'm gonna go through the rest of it now, I'll post about which other missions you need to purchase and how much they cost plus which level.
Looking To Boost on:
Resident Evil 5 (DE PRO)
Message me and send a F/R if you're interested.
I'm blackbelt at making a sandwich.