Well, I do not think the newer models are significantly more advanced than what you have, it's going to be significantly cheaper to repair your unit than replace (unless you go with a portable).
White smoke to me means oil. But backfiring means carb. Could be a gummed carb? Stuck choke? sticky valve or valve seat? I dunno, but I would not be surprised if a new carb and filters solved the problem. I'd start there. Actually, I'd probably start by running a can of Seafoam through it lol.
If that doesn't do it, I'd remove the whole unit myself and save at least some labor hours. Mine is just bolted up under the motorhome, unhook all the attachments and lower it with a jack. Then bring it to a small engine repair shop instead of an RV or Cummins shop. These are low tech engines.
