How to replace the expansion valve?

Thanks I'm having shop take refrigerated and rented vacuum to suck out the moisture. Also, I'm supposed to vacuum down after new repairs/replacement as well to pull any moisture that might have gotten into the open system, correct?

The only way to recharge the system that I have is the cans from auto store. Is that possible with the new compressor? Some compressors won't engage without charge pressure will this be an issue?

Will I need to add new pag oil or will the vacuum do that for me? How much pag oil or how do it tell?

Okay, kind of a crossover question. When replacing my compressor, evaporator, and dryer do I need to add oil or what's in the line should be good enough?

Ok so did the ac package. Once replaced expansion valve and vacuumed down it held vacuum over night. It took r134 fine and was blowing amazing cold air. Shut the car off and heard leaking saw it coming from expansion valve. I replaced the seals. Maybe didn't push lines in good and straight? Also there's this weird hexagon "port" I guess on the bottom of the valve is that just a spot to help hold in place. I didn't need to take out insulation around valve should I have to secure it? I have extra seals. I mean it was visiblely blowing out.

So vacuum done system, check rings, make sure lines are in straight and securely in place before screwing the bolts back in?

Maybe just didn't tighten bolts good enough?

Ok will take apart and take pics. The weird spot on the bottom doesn't do anything right? It's a weird but shaped hole with rubber on it will include pic of the old one when get back home. Thanks

Here's the bottom thing

Here's old expansion valve. First pic is front so line with ring goes into top hole and bottom hole line goes into with ring. Middle hole holds the lines in place and two side holes are for bolts. Most bolts for ac say don't overtighten. Do I tighten these more? I'll open system and take pics of current set up as well thanks.