Not exactly. in these situations they would bomb the GERD then ditch, out of fuel, in international waters ready to be picked up or in Sudan. It's been done before. For really high value targets range doesn't matter as much.
Which means they couldn't maneuver at all at the attack site, making themselves extremely vulnerable; Furthermore, a dam is an highly fortified target by nature, making serious damage requires very heavy bombs, not sure they could make it even as a one way trip if they are properly armed.
IMHO, most likely result of an attack (for Egypt) is that Egypt loses a part of its airforce in return for temporarily harming Ethiopia's ability to generate electricity at the site. At which point Ethiopia fills the dam anyway and works on repairing the damage, while Egypt wouldn't be able to repeat this.
They could certainly maneuver at the attack site - there is very limited depth for Ethiopian defences as the dam is only ten miles from the Sudanese border.
But yes, the planes would be expendable. That said, Egypt could very well breach the dam itself. It would needs some creative use of munitions but modern munitions are precise enough to allow for breaching of dams.
