To answer your first question, yes.
Originally Posted by Drummr3185
haha...ya Im pretty short, Im only 5 feet tall and in 8th grade lol...it doesnt bother me much...I got used to bein short
Cross country won't have any negative effect on height or puberty. It's just exercise and it will actually make you a lot healthier running so it will actually benefit you overall.
You still can get taller as you get older. You are only 13 overall.
Being tall isn't all that great either. I'm 6'5" and it can be inconvenient. Being short isn't the worst thing in the world either.