128:8 A mourner during the year of mourning for a parent should not lead the services on Rosh Hashana and Yom Kippur, nor should he blow shofar on Rosh Hashana, unless no one else as qualified to do so is available. If he is within the thirty days of mourning for one of his other relatives (shloshim), and if he is the one who usually leads the High Holiday services or blows shofar, then it is permitted for him to do so. This is because Rosh Hashana and Yom Kippur cancel the prohibitions of shloshim. However, if he does not usually do this and there is another person available who is just as qualified, then he should act stringently and not do it. (Mishnah Brurah 581:7 draws no distinction based on prior experience.) On all the days of selichos, however, even on erev Rosh Hashana (and during the ten days of repentance – MB ibid.), any mourner may lead the services as long as it is not during the week of shiva.
128:9 If one is saying selichos by himself, he may not say the Thirteen Attributes as a prayer or as a request; rather, he does so as if he were reading them from the Torah, using the appropriate tune. Also, any place where the Thirteen Attributes are mentioned in selichos, such as “remember for us this day the covenant of thirteen,” etc., should be skipped. Also, supplications that are written in Aramaic, such as, “He strikes and heals,” “Master in Heaven,” etc, are only recited with a minyan.