Planning to meet her finally!!

Hi all,
I am new to this forum. Looking for some help.
I want to know, can you go to Canada with a DUI?
I met my girlfriend online. We have been dating online for the past 8 months. She lives in Canada and I am from the US. So we have never personally met each other.
Now we wish to meet in person. She can’t come to the US due to some citizenship issues. She wants me to go to Canada. I am most happy to go and see her.
But there is a small problem.
A few years ago, I was convicted of driving under the influence of alcohol. When I was looking at the various Canadian laws, I got to know that you will be denied entry at the Canadian border if you have been convicted or just arrested for driving under the influence of alcohol or drugs.
But it’s been 4 years since the incident and I had served my term at the rehab.
I didn’t know that DUI was such a big offense that it would deny my entry into Canada.
Now, the past is past and nothing can be done about it.
I read that since it’s not been more than 5 years since the incident, the only available option is to apply for a Temporary resident permit.
I would like to know about this in detail. How long does it take to get me TRP? And can I apply directly or do I need to get the help of an attorney?
I want things to be done asap so that I can be in Canada and meet her.
Looking forward to your replies. Thanks.