Change value in XML tag using XSLT according to the attribute value

I am new to XSL and I am stuck with a problem.

I have an xml of the following format:

<Destinations>
    <conf:Destination id="12">
        <conf:attributes>
            <conf:attribute1>1212</conf:attribute1>
        </conf:attributes>
    </conf:Destination>
    <conf:Destination id="31">
        <conf:attributes>
            <conf:attribute1>3131</conf:attribute1>
        </conf:attributes>
    </conf:Destination>
</Destinations>

And say, I have an xsl with following 2 params:

<xsl:param name="attribute12" select="'21'" />
<xsl:param name="attribute31" select="'5'" />

I want to have a xsl template in XSLT 1 that changes my xml as follows: 1) For destination id=12 in xml, value inside 'conf:attribute1' tag to be set as 21 2) For destination id=31 in xml, value inside 'conf:attribute1' tag to be set as 5

This way I will have final xml as:

<Destinations>
    <conf:Destination id="12">
        <conf:attributes>
            <conf:attribute1>21</conf:attribute1>
        </conf:attributes>
    </conf:Destination>
    <conf:Destination id="31">
        <conf:attributes>
            <conf:attribute1>5</conf:attribute1>
        </conf:attributes>
    </conf:Destination>
</Destinations>

Can anybody please help.