If you use tweakflash to make your flash player show that its a linux desktop version you'll get the option to change the resolution above 240p but trust me, anything above 240 (even 360) will be choppy and slow since our flash player has no hardware acceleration. To watch high quality videos It's better to use something like qutetube, as mentioned.

Also, to upload videos, I think youtube has an option where you can email them videos (they give you a special email address, look in your options) and it'll upload them for you.