Apart from a 40-mile test in the Ford Fiesta RS WRC he is using this weekend, Tanak had not driven a current World Rally Car since the end of 2002.
The Estonian ended the opening day in Sweden in fourth place having set a fastest time and run third for three of the rally's seven stages.
"I didn't expect this," he told AUTOSPORT. "It's been a very good day. This morning I was just keeping the car in the line and driving sensibly.
"This is the first WRC event and the first event in a World Rally Car for my co-driver [Raigo Molder] - we weren't so confident before the start.
"Actually, I was shaking a little bit before the start."
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Tanak's first stage win of the season came on the second run through the Kirkenar test over the border in Norway.
"It was a good time," he said, "but I have not been pushing so hard this afternoon. I'm not taking any chances.
"I need to have some more miles in the car, it feels like I've been away for quite a long time."
Tanak was dropped by the M-Sport at the end of 2012 and he admits his year away from the sport made him more determined.
"I never gave up on this dream," he said, "and now I am back with the perfect programme."
Tanak will compete in Portugal and Italy in a Fiesta RS WRC before switching to a DMACK-backed Fiesta R5 in WRC2 for the remaining rounds of the series.