McNamara, a former winner of the top National Hunt jockey award at the week-long meeting, suffered life-changing injuries in a fall at Wexford in April 2015 and was left with no feeling in his lower body as a result.
He began training last year - saddling a double with his first two runners - and snapped up the Shamardal colt for €30,000 out of his former boss Dermot Weld's stable at the sales in November.
Sent off at 9-1, he defied a 276-day layoff to beat High Altitude by half a length in the Caulfield Industrial Irish EBF Maiden.
McNamara, who also owns the three-year-old, said: "If it had not been Galway he might not have run for another three or four weeks, he still has a bit of a belly on him. We've always thought an awful lot of him.
"There's a fair bit of improvement in him, but I still thought he would take a lot of beating. He does everything very well and he's bred to be a bit better than a maiden, he has plenty of class.
"He is one to look forward to, he's doing things well enough to be sold to Hong Kong or America, so we said we'd leave him as an entire for the time being and see how it works out.
"If someone came and left him in the yard it would be ideal, but I'm not going to turn down money for him if he's going abroad."
He added: "A few of the times I rode winners here in the past, I was a bit hazy coming back in (due to dehydration), but I'll remember this one, it was nice!
"The horses have been running well, I was looking and I was on the cold trainers list before today but the horses have been running really well and 15 of my 16 horses in the yard have been placed. Hopefully this is the start of more now.
"I probably preferred riding winners more as I was in more control, but I enjoy the daily life of being a trainer more. The buzz of riding a winner is a bit better, but training winners is very enjoyable also and I'll enjoy that for a lot longer than riding a winner."
Riven Light showed a sparkling turn of foot to win the feature on day two, the Colm Quinn BMW Mile Handicap.
A smart novice hurdler after joining Willie Mullins from France but only third on his first Flat start for the champion NH trainer, the five-year-old was dropped significantly in distance and was a well-backed 7-2 favourite in the Rich Ricci colours.
He still had plenty of horses in front of him entering the final quarter-mile but Declan McDonough found the gaps and although he had to force his way through, he had a willing partner, with Riven Light - who holds entries later in the week - quickening a length and a half clear of Iain Jardine's Hibou.
Fellow British raider Dream Walker was third, just ahead of Turbine.
McDonogh said: "He quickened well and was a very easy winner. I just had to sit and suffer for a little bit, but it's typical Galway, getting a little bit messy with horses getting a little bit tired, but I felt I was a good winner.
"In my opinion the gaps were there. The outside horses were pushing in a little bit and there was plenty of room for me to go."
Patrick Mullins, representing his father, said: "He got a superb ride from Declan, Ruby (Walsh) advised him to get there late and ride for luck and he pulled it off perfectly.
"It was a big decision by my father to drop him back to a mile, but he has always shown us a lot of speed at home and probably hasn't stayed over hurdles. It's good he is finally fulfilling what he shows us at home."
Shekiba built on a promising debut to land the Colm Quinn BMW Irish EBF Fillies Maiden.
A never-nearer fourth in the Curragh race won by Dawn Delivers at the Irish Oaks meeting, Joe Murphy's daughter of Arcano was allowed to go off at 9-1 for a contest that usually throws up a good one.
Murphy said: "She is entered in the Debutante (Stakes, at the Curragh later this month) and that will be her next run. She is a very tough, genuine filly and it looked a good race. She's definitely a Group filly."
Barry Geraghty made a successful return from injury in the opener on day one and repeated the feat on Housesofparliament in the Colm Quinn BMW Novice Hurdle, which got the second evening under way.
Geraghty struck on Le Richebourg on his first ride since breaking his arm in the Irish National and sporting the same colours of JP McManus, again for in-form trainer Joseph O'Brien, kept it relatively simple on the 11-4 chance, who was third in last year's St Leger at Doncaster.