Hi Ssnawin, don't let yourself be put off too much by DominicB's comments, he's actually an American who worked in a completely different field and now seems to enjoy coming on here and deterring people from coming to Poland from India etc for whatever reason. Here are some answers to your questions:
1.Can anyone let me know how much net amount will I get.
Depends on a few factors, however it should be around 4500pln
2.I'm married but I'm planning to come alone. Is the salary sufficient for 1 person.
3. where can I take apartment in Wroclaw for reasonable price, If everything works out for me.
Wroclaw isn't an expensive city, however you'll find that rents in the historic centre are more expensive. You will be able to find an apartment with easy travel to your work for a reasonable price. IBM is in the eastern part of the city and is easy to find an apartment near.
4. What is the living expenditure in Wroclaw.
That depends very much on you, whether you like to go out much and go shopping a lot, restaurants etc. 2000zl is a good figure however you could spend less or more.
5. Can we get our Indian food in Wroclaw.
There are some Indian restaurants. I'm not sure about shops, however you can get Indian spices, prepared mixes etc online within Poland. There will be other Indians at IBM who can advise what they do.
6. If I plan to change the job, Is it easy to get another job...
No - you'd need another work permit and an employer willing to sponsor this.