Should i swap my xr 125 for kmx 125?

hi i have a honda xr 125 on a 04 plate with tax and mot until january, it also has a micron exhaust on it my Friend wants me to swap him his kmx 125 on a 02 plate (black and red) very fast bike but has a few things needed to get it back to decent like it needs a new chain and front and back sprocket set as chain may be a bit stretched and back cog is worn, needs a new back tyre current is bald what do you think i should do? should i ask for his kmx and a bit of money to get these things repaired btw i really want a kmx but don't know weather to get this one or not kmx also has tax and mot until feb thanks!