From page 101 of Codex Imperial Knights:
The vehicle regains D3 lost wounds. If there is a TECH-PRIEST or TECHMARINE from your army on the Sacristan Forgeshrine...
Note that the rule is looking for specific keywords (since the words are in keyword bold). If the Techmarine Gunner has either of those specific keywords, then the answer is yes. If he has neither of those specific keywords, then the answer is no.