It won't burn the house down but it could toast a few coils, don't be afraid of the ground mods they aren't hard at all to do just take your time and follow the guides

System 80 games are good and can be pretty reliable. There are some things you should do and Clay's step by step process works pretty well. I have not done every single mod to every system 80 I have worked on though. I think system 80's get a bad rap personally and don't believe the hype.
A couple of things you should know is if the game is on do NOT remove and replace the board connectors and if you do not do the grounding mods you should at least do the "slam switch" mod. I have found that the slam switch without the mod can cause the most problems...in my experience.
Bottom line is don't let the "grounding" issues detour you from buying a Pin you are interested in, IMHO. Let us know what ya do. Good luck.

Ive had my battles with my black hole <also uses the same mpu> but most of the problems were dealing with battery corosion. I have installed a ni-waumpf mpu and i advise getting your original mpu rebuilt. They have a few quirks that ni-waumpf dont seem to care about fixing. Like im my black hole when the ball gets captured in the lower playfeild and you sink the last ball the machine hangs. You have to turn it off and the ball kicks out on bootup. Kinda sucks when you have just set the high score and you lose it because you turned it off.

The ground mods are not that hard to do. Any good with a soldering iron? I can not stress enough to fuse the pop bumpers before you do any repairs on the machine. JUST DO IT! I use 5 amp blade fuses on mine with nice holders. If they hang on the fuse pops in 5-7 seconds on mine. I had a big problem with pop bumpers locking on when i first got the machine and they can be updated and rebuilt to work better. I have a rotendog pop bumper driver board that PINMIKE sent me that works the same as the rebuilt oem boards. I think the oems pop harder i could be mistaken. The system 80s got alot of bad rap back in the days with the operators because of slam switches and coils locking on <bad design in pbdb>. I can go on and on but ill keep it short. There couple of people on here that will help with the sys80 including myself so just ask away.