Check the condition of the hose, it usually last longer than the bellows, but I’d replace it anyway if your going in. If this is a Bravo 2, yes you can change the hose without pulling the engine. If not, I’ll defer to others on the for7m.
It’s tight quarters, but there is room to pull the two bolts holding the inner hose fitting to the transom. You’ll then have access to the expander ring thingy-dingy. A special tool is needed for this ring. If you go this route, buy another expander ring and a gasket for the plate.
Also, I’ve done bellows with removing the gimbal ring as well as without. Definitely easier if you get the tool to remove the pins located under the trim sender & limit switch.
Use Merc bellows adhesive as well, letting it tack up before assembling and be sure the little metal tab is on the bottom of the bellows when installing. It has little teeth on the inner side and it adds just enough holding power to grip the horn so it doesn’t slide off while the adhesive sets up