Busbones.com has a partial how to do vw headliner install. Last 2 parts unavailable but lots of info. First you have to buy a good quality headliner. A few common handtools will come in handy. at this point you should also order new rubber seals for the front, rear and both quarter windows. The windows have to be removed in order to replace the headliner. The primary tool used will be a short blade putty knife (I used a bench grinder to dull the blade on mine so it would not cut the headliner fabric) which is used to tuck the fabric into the tabs that hold it in. There are steel rods called bows that fit through sleeves sewn into the headliner, these fit into tracks on the sides of the car's roof. The bows create the domed look of the headliner. You can start from the front or the back using clothes pins to hold the headliner in place so you can get things organized. You will have to pull the headliner tight and even so you do not have wrinckles. I used regular contact cement on my headliner and it worked great but you can use other types of adhesive if you want. After getting the headliner stretched front to rear you start on the sides. It is just about impossible to explain how to attache the sides, the best thing to do is to remove a headliner and pay attention to how it was installed. When you start take your time, getting in a hurry will only cause you to lower your quality standards and you will regret it later.
Look up on the headliner, real close to the front of the door. You should find a fairly good-size hole with two smaller holes, one to the front of the big hole, the other to the back of it. (If you don't, feel around on the headliner until you find the hole in the metal piece under the headliner, because someone replaced the headliner without cutting holes for the visors--which means YOU have to do it.) That's where the sunvisor goes. Stick the shank of the sunvisor in the big hole and attach it to the ceiling of your car with two screws.
more than likely you will have to take the back glass out to be able to slide the headliner out.
Begin by removing the wiring harness from the back of your 1974 Beetle blower motor. Remove the blower motor retaining bolts. Remove the blower motor fan. Reverse the process to install your new blower motor.
correct it will fit. be sure to take lots of pictures before you pull all of the wires off. so you have a diagram of where they go after.
Check the door jambs or fuel filler door - should be a label
There are specialty tools available to make this alot easier,piston ring expanders or pliers will help remove and install rings.
1974 was the first year of energy absorbing Beetle bumpers. You can't use earlier bumpers on 1974s.