I can't comment on I-80 west as I haven't been on it for a couple of years but when you get to Indiana it turns into a toll road. The Indiana Toll Road is in pretty good shape, they've been busy resurfacing it.
When I go to the Elkhart area I use I-94 east to exit 40 (Michigan City/LaPorte), taking 20 straight east to the bypass around South Bend (31/20). Staying on 20 all the way to La Grange (if I'm going to DRV). 20 is a four lane divided highway all the way to Middelbury where it turns into a regular two lane highway. It's used by LOTS of RVers and truckers avoiding the tolls. We were just out that way in July or August and it's an easy drive, with or without a trailer.
Good luck, from everything you're saying you're going to be making a trip to Goshen in the not too distant future!
Dan