i am in the final stage - my status has been adjusted but i am still without green card [its been 6 months since adjustment]. my employer is sponsoring me. can i marry a US citizen or will my entire process start over?

if you don't apply for any immigration benefits (visa, status) based on your marriage, marriage itself will have no effect on your current immigration situation.

In other words, as I see it, you can marry at any time.