GMC Repair: 98 Jimmy-Wiper Cowl and Braking, waterproof seals, wiper cowl

Question
Purchased a used Jimmy this winter, costs me $300 every other week to fix things. My newest dilemma is my husband put on new wipers and now the drivers wiper won't move properly, and has no tension when moved by hand. After hours of online search, a good idea is the linkage, but I don't know how to remove the cowl, and will I mess up any waterproof seals by removing the cowl without auto expertise?  My other dilemma which really needs to be fixed is the brakes but the mechanic doesn't know what to fix he said. Every so often under no specific circumstances, the brakes will not work. They make a buzzing or humming type noise, the brake pedal is completely locked. I can sometimes let off the brake and they work when I push again, sometimes I can go into neutral then back to drive and they will work, or there have been times where I was actually able to put the veh in park while still moving, and had to pull the emergency brake. I'm sure park wasn't the best choice, but going 25mph towards an intersection kinda knocks the sense out of you! Any ideas on what to guide him towards? Thanks So Much for your time and caring support...Ppl like me really appreciate it.

Answer
Hi
I first would not mess around with the brakes.....take it somewheres and have it PROFESSIONALLY diagnosed.
It is PROBABALLY in the abs system, but anything I told you would be strictly a guess.
The wiper, make sure the nut is TIGHT.
If it is then the wiper transmission (linkage) will need replacing.
You will not mess up any sealing surfaces etc... as there is none on that cowling plastic cover. all the sealing is done on seams.
I Hope this helps
Sorry for the delay
Pawl