Hareen, if you desire to perform an in-place upgrade to Linux Mint 18.2, it's much easier than say Windows & never once have I had troubles updating, although I always allow 2-3 weeks pass for any minor bugs to be worked out. Depending on CPU power, RAM amount, whether you have a HDD or SSD installed and finally, ISP speed, the upgrade can take as little as 5 to 20 minutes, with less than 10 being the norm for me.
The control for upgrade is actually in the Update Manager, if my memory serves correct, click the View tab & 18.2 will be offered. Note that unlike Windows, there's not a bunch of garbage left behind, Linux does an excellent job of tidying behind itself. In fact, so well that fragmentation is a non-issue, therefore no need to defrag.
One more piece of advice, do not run cleaners on your OS, examples are BleachBit & Computer Janitor, these can hose your OS in a split second. While there are a few temp files left behind, doesn't amount to a lot, and likely needed by one or more processes. The best way to keep your system clean is by clearing the browser cache at least weekly (more so if running a SSD), the system will take care of the rest.
While depending on setup, there may need to be minor tweaks made, usually nothing major at first, learn your way around & over time, you'll gain the skills you need not only for yourself, also to assist others who desires to make the leap as support for Windows 7 & 8.1 winds down & doesn't want to go with the ever buggy Windows 10 releases. The only reason why I run Windows are to assist others, can live w/out the problems, lots less maintenance with Linux compared to Windows (can't speak for Mac & Chromebook users). Although both of the latter mentioned are somewhat related to the Linux family, Chromebook OS's closer than Mac, although neither at this time are as secure, both has had their share of rounds of infections.
Take a peek in the security section, in particular in the 'Am I Infected' line, and see just how many Linux users are standing. My guess would be zero normally, however every now & then some thinks their OS may be infected when there's other issues to be addressed instead. Hopefully you've enabled the ufw Firewall as shown in my post above, and to take things a step further, read the manual of your router, if lost can be found online. Log in as instructed, using a computer connected by an Ethernet cable, and change name of network if default, all default passwords, to include Administrator, disable remote Administration & UP&P & enable the NAT Firewall if not already done. Security begins with the network connection, not that of the computer, although the ufw Firewall helps a lot, especially when in public.
Speaking of security & patching the OS, note that instead of one huge update per month, we may have a few small ones per week. Many are security related, and unlike waiting 3-4 weeks to be shipped, if a threat or backdoor is identified, the distros puts their differences to the side & releases a fix, usually within 24-72 hours after the issue was discovered.
Whenever you have a question, no matter how slight or large, feel free to create a new Topic at any time as necessary, we're here for you & if we don't have the answer, will do our best to find it. That's a common rookie mistake, not asking for assistance when needed the most, then turns around & bad mouths Linux when there was likely an easy solution. Yes there's a learning curve, yet it can be overcame by hanging in there and not being too shy (or too proud) to ask for a helping hand when needed the most. Every last one of us has been where you are at this very moment & likewise, none of us knows it all, that's why we solve issues as a community.