Well i dont really like salty or spicy food either so let me be your guide. My top favorite meat all time must be Bulgogi.
Its thinn slices of beef marinated that you grill and eat wrapped into lettuce and rice (often kimchi too if you like that).
The food is pretty sweet but not too sweet ... i would say PERFECT.

''I dont really get it ... whats the difference between Kimbap and Sushi?''
Well Sushirolls are basically raw fish rice and maybe some lettuce.
Kimbap is meat rice and vegetables ... also often served warm and sushi is always (or where i come from) served cold.
So yes it is a difference. Maybe they look the same but they dont really taste the same.

''Im going to Korea but im on a diet ... is all the Korean food salty and unhealthy?
I know they are not that fatty but very salty which is not good''
If your going to Korea on vacation i guess your gonna eat out (on a restaurant).
Most food are salty or fried in good restaurants but one dish that is common to find on menus are Soondubu jjigae.
Which is hot tofu stew served with rice but you can just take away the rice and the food is REALLY really healthy.
Another REALLY healthy one is Biji jjigae which is soybean stew.
(But this is not found on restaurants. Its very cheap so you can just buy it and cook it yourself)