Marriott doesn't have an option to use points to upgrade a "cash" or non-award stay. As for upgrading an award stay, it is up to the hotel whether they will offer (or take) points and/or cash upgrades. They don't have to offer upgraded rooms for points if they don't want to.

Normally, I will see cash and/or point upgrade options at hotels that tend to have a lot of upgrade options (i.e. resorts.) If a hotel doesn't show upgraded rooms available for awards, I have been successful in the past having the Plat agent call the hotel and ask about opening up an upgrade for points (or cash), but more often than not, the answer is no.