speedometer and fuel gauge are messed up!!!

[hondahunter180]

my speedometer will just say a rendom speed, like when i turn it on, it'll say 30 or 40 mph, when i start driving, it'll just peg out. the mileage is still accurate, this is why im confused. i thought the mileage was calculated using the speed sensor, so maybe its the wiring, i dont know. im going to get under it today and check the connection to the speed sensor, and ill probably change it out. but has anyone has this problem before? also, my fuel gauge will not work after it gets below half tank, but the fuel light still works. so maybe my cluster is just all messed up! if i get a new one, what do i do about the mileage? if anyone has any info for me i will appreciate it!