Do I need to worry about my seat post seizing?

Yes, seizing (or having the seat post stuck in the seat tube) is caused by a galvanic action between the steel seat tube and the aluminum in the alloy of the seat post. The best way to prevent this is to put a layer of grease or anti-seize between the steel and the alloy. The best way to do this is to coat the inside of the seat tube with the grease or anti-seize before inserting the seatpost. Remove and re-grease or reapply the anti-seize annually if not more often.