Anyone know how to change a Tx7 backup battery ?

Okay.. stange.. I somehow got my Tx7 working (meaning I opened it up,got confused, did nothing but give it a can of air cleaning, closed it, and it worked)
Given its age, I would still like to change the backup battery. I have another battery for it. My question is.. how do I get that stock battery out so I can replace it. I couldn't get it to budge and I couldnt see underneath it. Is it soldered to the board ? If any of you have replaced a Tx7 battery, please let me know how its done.
Thanks

Okay. Next question. I'm only using the Tx7 as a studio synth. If I keep all the patches stored on my computer and just dumped them into the unit as I needed and not careing as to wether they are gone when I turn the Tx7 back on again durring the next session, would I even have to bother with the battery replacement ? Does the unit become unusable when the battery goes or can I use it and it just won't keep user patches in memory after it's shut off ? This would not be a problem for me as I use a computer librarian full of patches for it. You will have to forgive me for asking so many questions as I am VERY new to this unit.