Don't be intimidated by changing out tires/tubes—very simple with a few tips. The best setup is if you have a waist-high trash can (or if you don't mind bending and squatting, a empty drywall bucket.) The idea being to have a work surface smaller in diameter than the rim that the hub will lie within so the support for the change is distributed around the spokes. Than be sure you get the majority of the air out by squeezing/pushing. If you pull the valve stem, all the better but not essential. Then get out the dishwasher liquid/water solution, fairly concentrated. (Use warm water to keep it comfortable if you're talking temps in the 30s.)

Then break the tire from the wheel rim on both sides by pushing down all arround. If the tire isn't free, pulling the tube or tire is a bear. The idea is that if you get one side of the tire rim as close to the center of the inside of the rim then you'll gain the most clearance opposite that point. (I've often been able to pop off a tire barehanded if the size/lubrication factor works out.) Once the seal of the tire has been released both sides all around, SOAP IT UP and begin at the point of greatest clearance. As you force the opposite side of the tire toward the rim center and if pry tools are needed, carefully slip the bar beneath the tire rim and be careful you don't pinch the tube. Pry up and above the wheel rim then, with the second pry bar, repeat near the first. Keep repeating, walking them along. At some point (not very far) the tire will hold itself and you can slip a your fingers in and lift the remainder.

With one side free it is easy to remove/insert a tube.

To get the whole tire off—once the tube is out repeat the prying sequence around the same side of the rim, the KEY being that the side opposite of the side that's being pried needs to be squeezed close to the center inside of the rim (the smallest diameter.) This gives the best clearance on the "action" side of the work.

The tip for getting it back together (assuming only one side of the tire has been released and only tube replacement is going on) is to begin inserting the slightly inflated tube (to keep pinching down) by securing the valve stem. Then starting at the stem point of the rim/tire, pop the tire in around both directions with the intent on meeting to pop the final bit of tire opposite the stem side. Again, the more you squeeze the tire inner beads toward the wheel inner circumference, the less force required to POP the last segment of the tire back into place. (Use the soap for reinstalling as well.) Now, once popped into place by hand or with prybar assistance, be sure to check to see no bit of tube is positioned between rim and tire prior to inflation. If the tube already was given slight inflation prior to slipping it back into the tire/rim, this shouldn't much matter. Slowly inflate and if all was positioned correctly the slippery tire will seat back into place around the rim. If you had removed the valve body from the stem and replaced to inflate, be sure to check it has seated well and not leaking with the soap solution. Hope this helps. This how I've replaced many tires and tubes. The bucket or can really helps in holding things for better control.

There are some commercially available little gems called "Bead Buddies" that you slip in between the tire bead and the rim to hold the bead loose while you maneuver your two tire irons around the wheel. I had good luck with cutting several wedges out of an old Frisbee, like pie wedges if you cut the Frisbee into eight equal pie sections. I carry a couple in the tool kit. I also used that rubberized dip for tool handles to coat the tips of the tire irons. This makes them hard to slide around between rim and tire bead but I always use soapy water to lube the tire. I add about a teaspoon of liquid dish soap to a Windex bottle and spray it on liberally. On the road, I carry a smaller spray bottle from insect repellent with the plastic top that fits over the sprayer. I duct tape
the plastic top to the bottle so it stays on in the tool kit.

Another old trick is to use a good sprinkling of baby powder inside the tire when mounting a new tube. This helps the tube to inflate evenly inside the tire. When filling it with air, I always go 10 to 20 psi over the required pressure, then drain it again, bounce the wheel a bit, then refill to the proper pressure.

One other item that I carry in my tool bag is a piece of closed cell high density foam, like from inside an equipment case. It makes a dandy waterproof kneeling pad. Mine is cut to fit the bottom of the tool bag, about 5" X 10" and is about 3/4" thick. It keeps the tools from bouncing around in the canvas bag, wearing a hole in it and beating up the paint on my rear frame.

AND... when reinstalling the tire, line it up so that it is in as close as possible a position, relative to the wheel, as it was before. This is so that you do not throw the balance off too much. For instance, see if there is lettering on the sidewall adjacent to the valve stem before you remove the tire. When placing it back on, line the same letter up with the valve stem and the thing may not shake or shimmy too bad until you get it rebalanced.