if it were me i'd download those two files that fail "Load.php" and "MessageIndex.php" and make the following edits to the respective file
In Load.php
Find:
AS post_group, mem.is_activated
Add after:
, mem.shop_nameStyle
Find:
pg.stars, mg.stars) AS stars
Add after:
, mem.shop_nameStyle
Find:
// What a monstrous array...
Add before:
// --- Begin modification - Display Name CSS item ---
$profile['name_style'] = (!empty($profile['shop_nameStyle'])) ? ('style=\'' . str_replace('\'', '', $profile['shop_nameStyle']) . '\' ') : '';
// --- End modification
In MessageIndex.php
Find:
ml.smileysEnabled AS lastSmileys
Add after:
, memf.shop_nameStyle
Find:
'link' => !empty($row['firstID_MEMBER']) ? '<a href="' . $scripturl . '?action=profile;u=' . $row['firstID_MEMBER'] . '" title="' . $txt[92] . ' ' . $row['firstDisplayName'] . '">' . $row['firstDisplayName'] . '</a>' : $row['firstDisplayName']
Replace with:
// Edited for Display Name CSS item
'link' => !empty($row['firstID_MEMBER']) ? '<a ' . ((!empty($row['shop_nameStyle'])) ? ('style=\'' . str_replace('\'', '', $row['shop_nameStyle']) . '\' ') : '') . 'href="' . $scripturl . '?action=profile;u=' . $row['firstID_MEMBER'] . '" title="' . $txt[92] . ' ' . $row['firstDisplayName'] . '">' . $row['firstDisplayName'] . '</a>' : $row['firstDisplayName']
Find:
'link' => '<a href="' . $scripturl . '?action=profile;u=' . $profile['ID_MEMBER'] . '" title="' . $txt[92] . ' ' . $profile['realName'] . '">' . $profile['realName'] . '</a>',
Replace with:
// Modified for Display Name CSS item
'link' => '<a ' . $profile['name_style'] . 'href="' . $scripturl . '?action=profile;u=' . $profile['ID_MEMBER'] . '" title="' . $txt[92] . ' ' . $profile['realName'] . '">' . $profile['realName'] . '</a>',
Then go through with the install and once it's done just upload the new Load.php and MessageIndex.php file you edited overwriting the old ones.