It's not a bad as it sounds:D
You need to tip the bike to the right side to put the filters back in...part of the process is filling the cases, where the filters go, half full of oil, you need the bike tipped to do this. I've got a rubber mat that I lay the bike on...no big deal. Funny, if you walk throught the pits at a Pro race...like Supercross, you see the Tech's with bikes on there sides all the time...I was horrified the first time now it's no big deal:)
And to answer your question, yes the 400 is the same. All the RFS bikes SX, EXC and MXC(400 or 520) use the same basic engine and the filters are the same.