The condition of my deck is just a little too ugly and I would benefit from another coat of color to hold it over a couple of years. Currently there is a solid color stain on it, and I want to know if it is reasonable to put another coat of solid color stain on it, or if there is a ton of prep that may not make it worth the effort.

Details:

Solid color stained, red
Located under a large oak tree that leaves dark dirt all over the deck
wood is in ok, but not quite good shape

I know I should prep using a deck cleaner, but if I want to stain again do I have to strip off all of the old stain first? If yes, would it be possible to coat with oil based paint instead?

I want this deck to only last another 5 years or so then I plan to remove/replace when I have some siding work done.