According to IMDb, there have been 3 movies, 2 TV movies, and one TV series called "Leap of Faith." But I'm guessing you're referring to the 1992 film starring Steve Martin. The soundtrack listing for that film includes "Change in my Life" performed by John Pagano. There is a soundtrack album, and it has been recorded by the Persuasions, by Rockapella, and by Sam Harris. (And there is at least one different gospel song called "Change in My Life.")

By listening to various sound samples available on CDNOW, I was able to confirm the correct wording: "There's a change in my life since you came along." Using this as a search argument in Google, I found several postings of the lyrics, which vary in minor details. I have posted what I think is the best one.

Copied from http://www.rockapella.com/LYRICS/changemy.txt

A CHANGE IN MY LIFE
(Billy Straus)

Standing cold and scared on top of Blue Hill,
There came one moment when I lost my will.
I prayed for mercy, "Lord, please take me away,
Or give me sunshine where I only see gray."
The past had a hold on me, it can't be denied,
And the changes didn't come easily.

CHO: I've been lonely, I've been cheated, I've been misunderstood.
I've been washed up, I've been put down, and told I'm no good.
But with you I belong, 'cause you helped me be strong.
There's a change in my life since you came along.

Now I don't mind working so hard every day,
And I don't pay no mind to what people say,
'Cause after all the pain I've been through,
Lord knows I'd give up everything just to love only you.
All my life I've held my head bent in shame,
But now I've found you, and with you I'll remain. CHO.

A man gets crazy when his world is all wrong,
And a heart gets weary when it doesn't belong.
When the road gets rocky, Lord, you've got to keep on.
Let the new light come shining on through. CHO.

Note: Some singers insert a line like "Oh, yeah. Oh, yeah. Yeah, yeah, yeah." at the end of each chorus.]

By the way, in the sound samples I listened to, the song is sung with a sort of gospel flavor, but except for the "I prayed…" line, there is nothing explicitly religious about it. The song as a whole could be construed as a prayer or hymn of praise, addressed to God, or it could be construed as a love song addressed to a lover, etc. I assume this ambiguity is deliberate. I wonder how many songs there are like this? It reminds me of a lot of Sufi lyrics in this respect. And then there's the Song of Solomon, which has been traditionally interpreted as an allegory…