It is very easy to get lower gearing on the Opus. Its crank has a 74mm bcd inner chainring. It will take a 24 tooth inner chainring. Have the shop put one on as part of the sale before you leave the store. Also put a 10 speed cassette on with 32 or 34 big cog. May have to go with a 11 tooth small cog. Have the shop do this before you leave the store as part of the sale. SRAM and Shimano make 10 speed cassettes with 32 or 34 teeth. MAY have to change the rear derailleur to a mountain derailleur. MAY. Shop can do this too before you leave the store. May not have to change the rear derailleur. Have to try it to see. 26x32 on the Trek is the same as 24x30 on the Opus. Identical low gearing. You can put down to a 22 inner ring on the Trek. Can go to a 34 cassette on both. Both bikes can easily get to very low gearing.
As an extra caution, put on a chain watcher. Mounts on the seattube below the front derailleur and has guides to keep the chain from coming off the inner chainring. Extra safety. Many models out there. Do a Google search on chain watchers.