Dead DX7 Mark I - Repair questions -- Help!

Hi there – Seth here, writing to you from Boston. After 20 years of just letting my DX7 Mark I sit in its case (I purchased back in the ‘80s), for the longest time I've been thinking about bringing it back to life largely as a MIDI controller – as the keybed is just incredible despite the DX7's weight – which would be tough per gigging. I'm hoping to use it like a Hammond B3 as I think the edges weren’t so sharp per waterfall techniques.
  
 I’ve pored through older messages in the forum here, I wanted to hear what you all thought as to the best way to go about getting started before I go down the rabbit hole per repairs. As I’m currently very frustrated per repairs with my other dead gear of the similar vintage, I just don’t want to drive myself crazy here – but I also don’t want this to end up in a landfill either. It was my first keyboard and I miss it all these years later.
  
 Again, it’s a DX7 Mark I with E! Grey Matter installed. All the DX7 ROM cartridges were lost somewhere in storage and I can’t find them – despite repeated attempts to recover them. 
  
 When I turn the DX7 on, I get 88 (or a different digit) that shows up, and dark blocks on the upper row of the LCD. I’m assuming that this means that the system isn’t booting? (Alternately – I’m concerned that this means the 9.4265 Mhz crystal may be dead…and I just learned that the company that made replacement crystals is out of business as of 2017!)
  
 So, I figured I’d (1) replace the battery (I’m good with soldering, so no problem there) using a fresh battery and an external CR2032 battery holder and then (2) try to check the connections with the E! and clean the contacts before reseating it. But I doubt these two things will fix it - but it's inexpensive enough to try.
  
 If that doesn’t work, I figured that next I’d remove E! and try to revert it to stock. But not having the original chips, I figured I’d ask to see if someone has the SER-7 ROM as a .bin file here that they'd be willing to email me; I’ve already ordered a EPROM burner for a totally separate repair so I could give that a go. (I figure that’s the best version EPROM to drop in there, especially per MIDI standards?) Also, if someone knows specifically what EPROM and RAM chip I should order and throw in there, that would be a help.
  
 But other than that, I’m out of ideas and I don’t have much money to throw at repairing this right now. Plus, again – I don’t have the DX7 ROM/RAM cartridges anymore, as they’re buried in storage – so I don’t know how I’d initialize the unit even if I could get it to boot - so that's another issue.
  
 
 Any thoughts or suggestions, I’m all ears. Thanks for your help!
 

 - Seth