Hey there. I'm new to cycling and these forums, and just bought my first bike since I was a kiddo. Before buying, I had done plenty of research online- Frustratingly, I felt that a cyclocross bike would be my best fit, but there just weren't any that would fit in my budget. My goal is to eventually be able to do my 4-mile daily commute on my bike, but also be able to do some VERY LIGHT trail rides on occasion (There aren't any of what I consider to be "real" MTB trails around here, sadly) - I was pretty sure a road bike wouldn't be able to handle the dirt/gravel/stones/grass/whatever I encountered on the places I planned to go, but I felt like a mountain bike would be overkill and harder to commute with, as I'm not trying to beat the bike up or tackle anything technical/etc, and so I was left rather confused and unsure of myself. After driving 4 hours (as there is no closer bike store that I could find) I felt like I couldn't go home empty-handed, too. The store owner was also trying his best to persuade me that "The best bike to own is a mountain bike"... So I ended up taking home a Trek Wahoo (Which probably doesn't fit me properly) and a few accessories (new seat!) for about $600 after a short test ride.

Anyway, finally getting to the point here. I feel like it's IMPOSSIBLE to move this bike uphill, even when there's only a 5-10 degree incline and I drop down to first gear, it kills me. It's gotten SLIGHTLY easier as I've been riding at least every other day for the 3 weeks that I've owned the bike, but right now it seems like my 4-mile commute is not realistic at all, which is pretty embarrassing... Conversely, it feels like I'm riding a motorcycle going back the other way; the bike flies downhill, so I guess that means the tires roll well... Which is why I'm not getting how going "up" is so tough.

While I haven't exactly been active up until owning the bike, (*cough*, I'm a bit out of shape) I'm not overweight and I've really been trying to push myself when I ride, not stopping until I'm out of breath and totally exhausted... I've fallen over once while trying to walk down the sidewalk to my house after parking and locking up my bike because my legs were so shaky.

So my question is... Will switching out my rather-knobby stock tires be the cure for all of my problems riding on road? If so what tires should I look into (keeping in mind that I want to take to the light dirt/gravel/grass trails once in a while), will I need wheels, and most importantly, will I be able to switch everything by myself? (hopefully with the help of some youtube videos, of course)

I believe these are what's on my bike: http://www.singlespeed.nl/catalog/images/bon292.jpg Bontrager 29-1, 29x2.1"

Thanks for reading... The answer might be that I'm just too out of shape. I'm not trying to make excuses, so please tell me if you think that's the case. I just wish I knew how long it'd take me to get into shape for my sissy 4-mile commute as I'm a bit sick of carpooling and borrowing cars and think cycling would be great fun if it wasn't so frustrating for me right now.