It sounds like Helpdesk need to have a proper look at your account, as something is not right there.
To create a new consist, create the train first (using the normal methods) then use the Get tool on the Train - Consists page (it should then ask what you want to call it)
As for changing engines, you can do so by placing the consist, then use the tools to add and delete single train parts to remove the engine and place the new one - note though, that this will not change the original consist in the Consist list.
Shane
