Wasn't that hard.
Had to cut out dividers in the battery tub on one side so the new battery would sit flush. Had to remove the On-board computer and connect a couple of wires together. Had to replace the charging receptacle and run the battery gauge cable to the dash and mount the gauge.
All in all, it took me about 4 hours. There are several you tube videos on how to do it.
All in with battery, charger, and 48V converter it was $2300. Since I plan on keeping the cart for a long while and lead acid batteries only last 5 years it was worth it to me. Lithium should last me 10-12 years.
Other benefits are that you can charge the battery at any level. You can turn the battery off when not in use. You can charge it anywhere as long as you have access to 110V. The gauge tells you how much battery you have left (analog gauges are wonky IMO).
Most important it gives my wife peace of mind hauling my grandkids around knowing that the batteries won't go dead.