I'm in Mexico. A little back story: took my 98 VW Bug for repair, it's been 8 months and still don't have the car, took the mechanic to "alternative justice" (which meant having a mediator to find a solution before taking things to small claims, and now has until August 27th to have the car ready. With this, I'll be receiving a form with everything done to the car, and will have to sign after testing the vehicle.
Because of this issue I'm now concerned with how I will receive my car.
Besides taking the car to another mechanic to have it checked, testing it myself, what else can I do? Is there something in specific I should tell the second mechanic or how I should test the car?
This "mechanic" that you sent it to is not an actual car mechanic. There's a good chance that your car might get wrecked after you get it back.
If it's not severe, you should tell the second mechanic that he didn't know what he was doing and that they've never worked on a car before.
Yo tuve una situación similar hace años con un vochito. Se lo llevé a un wey para que lo arreglara y se lo quedó un par de meses, y cada que llamaba me daba largas. Un dia me harté y le llamé, le dije que iría esa misma noche por él auto, que mas le valía que encendiera. Fui con unos amigos y a la mala nos llevamos mi carrito. Estaba en un estado deplorable, prendió pero se mató a medio camino. No arreglamos nada con el dizque mecánico, el aprendizaje fue que desde ahora investigo muy bien con quien llevo mis autos, y de preferencia hago yo mismo las cosas.
Te sugiero que hagas lo mismo, acepta el auto como está y deja todo así. No le vas a ganar a esos canallas. Ojalá todo vaya bien, ánimo!