You should be able to pry open the case using your guitar cable. That's what it is designed for.
Anyway ... I love my DF-7 especially the DOD 250 and MT2 settings which I think sound better than the originals. I don't use the DS-1, TS, Rat and BIg Muff settings. The DS-1 emu is definitely meatier than the Boss DS-1 MIJ and it has more gain but I generally don't like the DS-1 anyway so.... The original Tube Screamer sounds so much better imho. No comments on the Rat and Big Muff settings. Didn't have the chance to A/B them.
When chained to the GDI 21, it sounds really good even with a 40W transistor combo. The mixer out works great when plugged straight into the PA. I also use that output when recording to my computer.