trans. problem/what to do, whats wrong with it?

Hey all, my engine now sounds different(like a weedwacker) just before i start to shift into diff. gears. Like from 1st to 2nd, at like 15mph, it starts to not sound normal and starts to sound like a weedwacker. THen, from 2nd to 3rd at like 30mph, etc. etc. This all started to sound bad as soon as my 2nd gear started to grind when shifting. Whenever i go into 2nd gear, there is some friction. Is this somehow related? i have a feeling yes...i dont know too much bout cars, so how much do you guys think it will cost to get a trans. rebuild? and will this help fix that weedwacker sound? Thanks a lot