Do not use PayPal Friend and Family, or any way that is not trackable (money orders, etc). Sellers, include the fee, and buyers don't do business with someone emails you off the site.
All Tikka T3/T3X actions are the same. Long or short action is determined by the bolt stop. Any T3/T3X Action will fit, but the mini chassis is for short action mags, so if running a long action round, you would have to single feed.