My turn signal will work occassionally and stop. I try it all the time but sometimes it works and sometimes it doesn't. I checked the fuse but it seems alright. Some sites said to change the relay? Switch? are they the same? Where and how would I change it?

On cold days my car will change into the highest gear no problem other times intermittedly it will only go into 3rd gear (normally on hot days)? What can I do and would I be able to fix it myself, being slightly mechanically inclined for troubleshooting but not a real heavy duty mechanic.

Thank you for your help and support.