[R] estimation problem

[Kehl Dániel]

Dear List-members,

I have a problem where I have to estimate a mean, or a sum of a 
population but for some reason it contains a huge amount of zeros.
I cannot give real data but I constructed a toy example as follows

N1 <- 100000
N2 <- 3000
x1 <- rep(0,N1)
x2 <- rnorm(N2,300,100)
x <- c(x1,x2)

n <- 1000

x_sample <- sample(x,n,replace=FALSE)

I want to estimate the sum of x based on x_sample (not knowing N1 and N2 
but their sum (N) only).
The sample mean has a huge standard deviation I am looking for a better 
estimator.
I was thinking about trimmed (or "left trimmed" as my numbers are all 
positive) means or something similar,
but if I calculate trimmed mean I do not know N2 to multiply with.

Do you have any idea or could you give me some insight?

Thanks a lot:
Daniel