Revitalized Late 2013 iMac
iMac was very slow after modern OS upgrades and I attempted software means to fix. A friend recommended ssd upgrade had helped. I decided to do a RAM upgrade at same time. I wish I done this sooner. Probably would recommend someone buying a used iMac to do this.
Intense but not hard. Lots of good YouTube videos to walk you through the process. SSD is very doable, getting to the RAM offered more obstacles (doubled time). Tools supplied worked well
Take your time. Kept screws and parts organized on back of old print outs marked with type. Screen adhesive remover was worth it though it can be done without.