The bridge and rocks are quite easy to do.  There are growth trees in Carrara (you can modify the trunks and leaves).  Making realistic water in Carrara is more difficult.  Grass, I think that some folks here can show you how to do that (I can't).

I would click on help upper shelf, then Carrara help, grab some Cnoffee (that's industrial coffee), start reading and doing.  The sick feeling in the pit of your stomach will gradually go away after all it did in Poser didn't it?  Jan