Carver Water heater + lost in translation....

We have an 18 yr old Carver Cascade water heater in our caravan. It's stopped working on the gas side. While we've had some advice from Gary who seems to the be one oracle of things Carver, our engineer is very reluctant to tinker with it for fear of breaking old parts and losing the electric function too.
He mentioned the possibility, while expensive, of fitting a Truma replacement. I think he reckoned the Henry replacements for Carver weren't up to much. ( ...?)

Any comments on the success of fitting a Truma would be welcome, please. Or we can just go on using the kettle if we're off EHU - there's no shower in the van, nor built in heating, to need hot water.
Is there a good source of reconditioned Truma 2nd hand units?

Suggestions for other brand reliable replacements also welcomed, please.

Meanwhile, for your entertainment, here's what one site says on the matter. I can only guess how many automatic translations it's gone through to get here:

"At normal you are using cascade little hot water to arrive at your shower temp. Health in the office is more important, and therefore you can consider investing in this ergonomic water chair.
Windguard for Truma boiler. This may not be element easy normal it sounds.
Flue extension VBO 2, heater 50 mm for wall thickness over 35 water necessary. Philips head screwdriver,20mm,17mm spanners,electrical screwdriver,flat head screwdriver. Loading prices, please wait A socket can be used but carver valve cascade too close to the element housing heater you will put pressure on the threads and they may snap.

This usually carver much less than one working water."

That makes it so much clearer, then.... ( https://waterheaterforum.club/heater-clearances/carver-cascade-2-water-heater-element.php  )