URL Rewrite Rules Help

[CharlieDelta]

Looking for some help with url rewrite rules from someone who is far more proficient than myself. I know nothing.

Old domain = www.canadianriflesregiment.com
Now domain = www.crrgaming.com

I changed domain names and want to ensure all urls get redirected properly.
I want to ensure that all urls get redirected with www. So for example if you type
canadianriflesregiment.com
or
crrgaming.com
you go to
www.crrgaming.com/crrforums/
I also want to ensure that all urls get directed to with the "/crrforums/". For example if you type in
www.canadianriflesregiment.com
or
www.crrgaming.com
you go to
www.crrgaming.com/crrforums.

I did just recently receive an email from paypal telling me of a IPN being sent to a URL that is failing and I think it may be due to bad rewrites =
http://www.canadianriflesregiment.com/crrforums/payment_gateway.php?method=paypal