Welcome to iRV2.
Furnace blower motor noise is a common problem . Motor replacement is a slightly fiddly job , but requires very few tools.
My furnace ; Suburban 42S ; took around 2 1/2 hours , but I just lubed the motor bushings instead of replacing , so that added to the time .
If you could add the year of your RV to the post , I'll look up info on your furnace to see how close the two furnaces are.