Saving Taxonomy Terms

I have an interesting problem which I hope someone can quickly answer.

I have created my own metabox which, based on “MY METABOX CODE” (list below) is correctly displaying a dropdown list of all my terms within the “event_types” taxonomy I created.

Where I am running into an issue is being able to SAVE/UPDATE the term associated with a post when a different term is selected from the dropdown and the post is updated.

After tinkering around with various code bits I was able to figure out that by MANUALLY entering the term_ID number(s) [separated by commas] into the array area I am getting the results I am looking for.

For example if on saving the post a function were to call this code

wp_set_post_terms( $post_id, array(5,7), 'event_types', FALSE);

then my post WILL UPDATE and associate the term_ID 5 & 7 to it which as you can see I am passing in the array. The problem is that this is hard coded into my functions.php file and not based on a user selected dropdown value (note: I am actually only trying to pass one ID but I did two for testing as explained below).

I have also been able to figure out that if I add the following code to my metabox file then I am able to echo a list of assigned term IDs but the last item has a comma.

<?php $event_types = wp_get_object_terms($post->ID, 'event_types'); 
foreach ($event_types as $event_type) { echo $event_type->term_id . ','; } ?>

So… it seems I have 85% of my problem solved. The Remaining 15% of my problem remains as follows:

1. What do I need to add to my functions.php file code (listed below) so that when I create/update a post the NEW VALUE selected from my taxonomy dropdown list is passed into the array?

2. Although in this example I am looking to ensure that only a SINGLE taxonomy can be associated with a post, there are other situations where I would like to create a checkbox list which would require me to pass more than one value into the array. As such, what would I need to change so that a comma separated list of term IDs is passed into the array? If your answer involves using some or part of the example code I listed above where I echo the IDs then how do I ensure the last ID which is printed does not have a comma at the end? (Is there a different/better way to do it? I saw hints which might relate to adding a filter but I am not sure how this is done…)

Thank you guys very much in advance – below is the code I am currently using in each file.

CODE IN MY FUNCTIONS.PHP FILE

function save_event_taxonomy_terms($meta, $post_id) {
        $event_types = wp_get_object_terms($post->ID, 'event_types'); 
        wp_set_post_terms( $post_id, array($names), 'event_types', FALSE);
    }

MY METABOX CODE

<select name='post_event_types' id='post_event-types'>
// DISPLAY TERMS AS DROP DOWN OPTIONS
    <?php 
    $names = wp_get_object_terms($post->ID, 'event_types'); 
    $event_types = get_terms('event_types', 'hide_empty=0'); 
    ?>
    <option class='event_type-option' value='' <?php if (!count($names)) echo "selected";?>>Not Assigned</option>
    <?php foreach ($event_types as $event_type) {
        if (!is_wp_error($names) && !empty($names) && !strcmp($event_type->slug, $names[0]->slug)) 
        echo "<option class='event_type-option' value='" . $event_type->slug . "' selected>" . $event_type->name . "</option>n"; 
        else
        echo "<option class='event_type-option' value='" . $event_type->slug . "'>" . $event_type->name . "</option>n"; 
    }
    ?>
</select>