The process for high score save kits varies from board to board.
On some game boards the chips that need to be changed to install other chips, or an add-on card are socketed. So no soldering is required. On other boards, chips may be soldered in place and would need to be removed and sockets installed for a high score kit. There's no rule of thumb here, you would need to look into each game you wanted to do this to as the process is different for each game.
Now, if I recall. To do the high score save on a Super Pac, two eproms will need to be changed, there are usually socketed to that's easy. But I think one of the SRAM chips needs to be changed out as well with a new Dallas one. These are *usually* soldered on the board. You may want to find somebody with experience soldering to do that one. IC's are not the easiest thing to get off a board and, if done improperly can damage the board.
Regards,
D