Hi Jaquie,
Yes, we have gerund in Spanish. The ending is -ndo, ando for verbs of the first conjugation, second and third -iendo: hablando, comiendo... But the usage is not always the same as in English, for example an action like in your example :"Running is not a sport I like by itself,.."
would be in infinitive:"Correr no es un deporte que me guste en sí mismo...
It is mainly used, like in English, in the present continous: Estoy comiendo ( I am eating).
Regardind your second quiestion is a NO, You don´t add a pronoun to the end of a cojugated verb, you just add to impersonals forms of the verb (imperative, inifinitive gerund). Examples.
Vete, Poderme, Decirte, Lavándose...