1.わたしはあるくのはいやです I hate to walk. - might prefer take a bus, taxi, or something.
2.わたしはあるくのがいやです I hate to walk. - just don't want to 'walk’
In this case, 「~は」implies there are some options, 「~が」emphasizes ’~’.
3.わたしはあるくのをえんりょします I would rather not walk. ( えんりょする is a polite way to refuse)
「を」is objective use.
Usually,「です」comes after nouns, pronouns, adjectives. 「ます」comes after verbs.