Casts spells as a 5th level...

[Invader]

If you have a playable race with a LA or a monster that can cast spells as say a 5th level cleric and then you take a level of cleric does that progress you cleric spell level to 6th level and cleric class abilities to 1st level. Or is a race/monster that "casts as..." not progressed by taking more levels in a class?

[lunar2]

casting ability (or equivalent mechanic, such as psionics) stacks, unless noted otherwise. class features do not stack, unless noted otherwise (a rakshasa gets a familiar as if it were a sorcerer of its caster level if it has a level of sorcerer).