They can be installed without the tool if you know what you are doing but it's not an easy job and it's easy to get hurt if the spring get away from you. Tool makes it much easier and safer.
Yes you can just use them in the rear for the extra weight. You can always do the front later if you don't like how the bike sits or handles.
Yes you can just use them in the rear for the extra weight. You can always do the front later if you don't like how the bike sits or handles.