Traveling before receiving the green card

[EgFalcon]

I have just received my immigrant visa package (spouse of an American citizen), but I have a job in my country, so I have to enter the USA before the visa expires, then return back to complete my contract that ends in 8 months.

How long does it take to complete my first entrance to the USA? few days, weeks, or months? (I will not wait for the green card, but is there any other thing to do, like medical exams or paper works?)
Are there any steps required before traveling from the USA and before having the green card issued?

Many thanks for the help

[newacct]

You can leave the same day after you enter if you want.

[GAURAV THOSANI]

Pay immigrant fee as early as possible so u can get green card as fast as possible