'Sewage ejector' system is a generic term that can mean an above-ground unit or an inground unit.
The above-ground units are easier to install, but have smaller discharges and inlets and are prone to clogging (that's what I read, at least). Also, you're limited in yr choice of toilets to rear-discharge ones. However, with clever placement, the unit can be hidden behind a wall and yr bathroom will 'look' just like a regular one - except for the shower, which will have to be on a platform.
The in-ground units are more bigger and more powerful, which means fewer clogs and a longer life. However, these require concrete excavation. Concrete digging is not hard if you don't mind dust-I mean a lot of dust, have a strong back, and if your water table is fairly low.
You can have a handyman jack the 'crete for a fraction of the $3000-6000 a plumber might charge to do the whole rough job (which might be your best option since they'll route yr water supplies and vent too).