There's quite a lot of difference between the way the dialects pronounce things sometimes - for ex. in Munster "déanamh" is "daynuv", in Ulster "jannoo" - but if you're broadly familiar with how each dialect pronounces things you can understand them, and to sound natural you only need to know how to pronounce one dialect. There are some grammatical and vocabulary differences between the dialects as well, but they're not very big, and the written language is pretty uniform across all the dialects.
There's an official standard grammar - the Caighdeán Oifigiúil - but no standard pronunciation.
Here are a couple of web pages about dialect differences: http://www.smo.uhi.ac.uk/gaeilge/gramadach/canuinti.html http://www.ling.uni-potsdam.de/~green/canuinti.htm
They might be a bit technical though.
Your parents would be ideal people to copy the pronunciation of, if you can get them to speak Irish to you - it's a shame they didn't bring you up speaking it, being raised bilingual never did anyone any harm ever and is even beneficial to people's command of both languages, apparently - but if they speak different dialects, pick one and stick to it. It'd sound a bit odd if you mixed different dialects' pronunciations.
I suppose you might describe Ulster as "harsher" than other dialects, but that's probably more a matter of intonation than anything else and besides, the person's voice who's speaking will almost certainly make a lot more difference than the dialect. Connacht (the western dialect) is the strongest in terms of number of speakers in Ireland, but the pronunciation is I think the hardest to learn.
Ádh mór, (good luck)