[Card Exchanger help]

Hello

Everything is working fine with the script. I would like a small modification though.

At case 4:

Instead of accepting 5 card coins for a random card -> open a shop where I can use Gold Coins as currency

I would appreciate the help as Im sitting on this thingy since an hour and dunno what to do

//===== rAthena Script =======================================
//= Card Exchanger
//===== By: ==================================================
//= Euphy
//===== Current Version: =====================================
//= 1.0
//===== Compatible With: =====================================
//= rAthena Project
//===== Description: =========================================
//= [Official Conversion]
//= Exchange any card for a Card Coin, and 5 Card Coins for
//= a random card in exchange.
//=
//= NOTE: This NPC is only available in pRO and twRO.
//===== Additional Comments: =================================
//= 1.0 First version. [Euphy]
//============================================================

// Main NPC :: Card_Change_tw
//============================================================
prontera,158,179,4	script	Card Vendor Machine#pa08	10343,{
	if (checkweight(1201,1) == 0) {
		mes "You have too many items, please reduce it and come back later!";
		close;
	}
	if (MaxWeight - Weight < 1000) {
		mes "You are overweight now, please reduce it and come back later!";
		close;
	}
	mes "[Terminator RX1]";
	cutin "shiki01.bmp",2;
	mes "Text Explanation Begins:";
	mes "Press 1 for Cancel,";
	mes "Press 2 for Explanation,";
	mes "Press 3 for Coin Exchange,";
	mes "Press 4 for Card Exchange.";
	next;
	switch(select("1.Cancel:2.Explanation:3.Change Card into Coin:4.Change Coin into Card:^ffffff5.Start Security System^000000")) {
	case 1:
		mes "[Terminator RX1]";
		mes "You are welcome!";
		close;
	case 2:
		mes "[Terminator RX1]";
		mes "No.3, when you choose Coin Exchange, system will collect ONE card from your inventory randomly to exchange into ONE Coin.";
		next;
		mes "[Terminator RX1]";
		mes "No.4, when you choose Card Excahnge, system will collect FIVE coin from your inventory to exchange into ONE Card randomly.";
		next;
		mes "[Terminator RX1]";
		mes "You are welcome!";
		close;
	case 3:
		specialeffect2 EF_COIN;
		specialeffect2 EF_LOUD;
		progressbar "0xffff00",3;
		callsub L_Exchange,	// yes, this list is hardcoded in the official script...
 60137, 
 60138, 
 60139, 
 60140, 
 60141, 
 60142, 
 60143, 
 60147, 
 60148, 
 60149, 
 60150, 
 60151, 
 60152, 
 60153; 
        
		
		mes "[Terminator RX1]";
		mes "Card searching has finished!";
		next;
		mes "[Terminator RX1]";
		mes "Thank you for coming!";
		close;
	case 4:
		specialeffect2 EF_COIN;
		specialeffect2 EF_LOUD;
		progressbar "0xffff00",3;
		if (countitem(6379) < 5) {
			mes "[Terminator RX1]";
			mes "You do not have enough coins.";
			close;
		}
		delitem 6379,5; //Card_Coin
		.@r = rand(1,34261);
		     if (.@r <= 2001)  getitem 4001,1; //Poring_Card
		else if (.@r <= 34259) getitem 4440,1; //Necromancer_Card
		else if (.@r <= 34261) {
			if (rand(1,10) == 1)
				getitem 4396,1; //Tha_Odium_Card
			else
				getitem 4092,1; //Skel_Worker_Card
		}
		mes "[Terminator RX1]";
		mes "All cards have finished.";
		next;
		mes "[Terminator RX1]";
		mes "Thank you for coming!";
		close;
	case 5:
		mes "[Terminator RX1]";
		mes "Found unauthorized signal, starting security system...";
		close2;
		warp "comodo",263,286;
		end;
	}
	close;

L_Exchange:
	freeloop(1);
	.@args = getargcount();
	for (.@i = 0; .@i < .@args; .@i++) {
		if (countitem(getarg(.@i))) {
			mes "Found ^980078" + getitemname(getarg(.@i)) + "^000000,";
			mes "Do you want to exchange ONE Card into ONE Coin?";
			next;
			switch(select("No:Yes")) {
			case 1:
				mes "^980078Do you want search for other cards?^000000";
				next;
				if(select("No:Yes") == 1) {
					mes "^980078Card searching is interrupted^000000";
					close;
				}
				break;
			case 2:
				if (countitem(getarg(.@i))) {
					delitem getarg(.@i),1;
					getitem 6379,1; //Card_Coin
					mes "^980078" + getitemname(getarg(.@i)) + " has exchanged into Coin.^000000";
					next;
				} else {
					mes "^980078Your inventory does not contain the card for exchange.^000000";
					next;
				}
				break;
			}
		}
	}
	freeloop(0);
	return;
}