From your discription I think you are working on a 5S-FE engine. How you take the seal out is not a real problem. You really don't need a special tool to do this. You may follow Runtao Ye's recommendation to remove it with a small screw and a flat head srewdriver to pry it out. The metal there is very hard and you will not likely damage anything if you do it carefully.
Your real fun begins when you try to put the new seal in if you do not have a special tool for it, since you already mentioned that the space was tight and excess is limited. You need to press the seal in evenly and make it flush with the metal edge. I don't think I can do it without a tool. You can google "cam seal installation tool" and sea a picture of this simple tool. One picture is worth a thousand words. You see it and you'll know how to use it. Since this is your first time DIY on this, and you have been doing well so far, I respect your mentality and hands-on ability. I'd like to offer any help possible.
You may question if I know what I am talking about. I make bold to talk about it because I did this several times.
