If you deleted any word from your file and pressed the "OK" button then the file has changed with the deleted part with this i can't help you but check into your folder maybe you have only UNLOADED and not deleted because you said you don't know very well about scripts. If the file exists try using the /load command for more write (/help /load) in mIRC.
Now in the second that you said to take over your PC from mIRC, I am not very sure and i haven't see it since now that but i know if you have not any FIREWALL installed into your computer then a HACKER could be insert into your system and take over your PC, Also if you have not installed any FIREWALL and you don't want to, just disable the DCC from the "mIRC options" click on the "DCC" section and dislable it!
thank you so much for your reply dear westor. ^^
you know I am not quite sure did I click the OK button or not and that's why I am this scared about accidentally changing the remote script.

I read some people can have total control on your PC and files if you let them through adding a line of a particular command to the remote script. they can send virus or trojan to your system or even have control on your hard drives and etc. and may I ask which folder should I look into? I checked my IRC folder and I just found log files from chats and uploaded files. is there a log file which can let you know your script has changed?
about firewalls, my windows firewall is off but I have an updated/registered version of NOD32 which includes fire wall, anti spyware and anti virus. it works pretty good but since this is the first time I have such a problem, I wonder if some one tries to hack my system through IRC, can NOD32 catch it? :-s and if I disable my DCC then does it mean even if my remote script has changed, yet no one can sent a file to me or find a way to hack my system?
I am so sorry if I asked too many repetitive or probably obvious questions. to be honest I am not planing to use scripts right now, those look difficult and I am just a newbie regarding IRC and still learning about it. all I want is to keep my system secure and safe. if I know by reinstalling mIRC I can stop hackers from accessing my PC I would do it without hesitation.