The assistants available (Kiss, RGMercs, CWTN Class plugins, and others) differ greatly in how much fine-tuning you will need to do.
For one example, Kiss uses ini files, and when you level and get new spells, you must edit the ini to change your spell set up. This is not difficult for a person who is comfortable with editing text files, and once you get the swing of things, it's not that annoying. Kiss uses "modes", so you would set your puller to Puller and your tank to Tank. There are other modes. I believe Kiss is free if you have a Level 2 sub here on Redguides.
I have no experience with RGMercs.
CWTN Class plugins, for example MQ2Mage, work out of the box. They know the spells you should have and how to use them. CWTN also uses modes, for pulling, tanking and other stuff. They are not free except on the Test server. A great way to play around with the CWTN plugins is to make a couple of characters on Test and fool around.
Have fun in your explorations!