Hey hello I'm doin my heater core in my 3 myself but Im havin a tough time with this thing here.. the blower motor housing I think she's called. It just wiggles but not much else.. and with the effort it took to get the old core out I don't wanna force the new one in. If anyone's dealt with this before or maybe just has a fresh idea that'd be really helpful.. http://imgur.com/q8dKrOo

 

I'm not sure how you exactly forced the old one out, but heater core replacement on a 3, requires complete removal of the dash. I've seen it take about a week for the DIY at home in his spare time. Nuts, bolts, time and patience.