This is the first marriage for both, and they have been married for decades. Catholic spouse did not know about dispensations but did marry a Christian in a church by a pastor in a traditional wedding. Been given different labels for their marriage, that it is invalid and they need to get married again, have to go through a marriage prep class, that a dispensation has to be applied for because one spouse is not Catholic yet, but is willing now to go through RCIA. Also been told a convalidation is simple, should take 5 minutes. Definition of Radical Sanitation sounds like their marriage would be considered valid from the time it took place originally since they have been married for decades and they would not need to be dragged all through these applications. So which is it?
The marriage is invalid. A Catholic is obligated to be married in the Church or receive a dispensation to be married elsewhere. Ignorance of the law, in this case, does not excuse from the law.
They shouldn’t need to do marriage preparation classes, I don’t know of any American diocese that requires them for couples that are already civilly married.
Validation is a relatively simple process. They need to bring their proof of baptisms and proof of their civil marriage. There will be a little bit of paperwork for permission for a mixed marriage since her husband is a baptized non-Catholic, it will just be rolled up into the validation paperwork.
A radical sanation is not the route to go, a validation would actually be simpler.