I received an email (via GMail) containing single URL link. For the purpose of this question, it is irrelevant whether link came from someone I know, because origin can be spoofed or faked.
More or less. GMail does a pretty good job filtering spoofed email addresses, as long as the corresponding domains have DKIM and/or SPF set up.
Of course, anybody with access to the email account (e.g., malware) can still send those mails, but that's different form header spoofing.
That means that if the link points to some malicious site, either your friend's email account has been compromised or you shouldn't call him a friend. In either case, contact him (preferably not via email).
How can I verify that the link points to some some virus/trojan/malware? It there software that helps me to verify this without endangering my PC?
A website can only infect your computer if it exploits some vulnerability in your web browser or – much likelier – one of its plug-ins.
In Google Chrome, e.g., you can set Plug-ins to Click to play in
chrome://settings/content, so you have to give your permission explicitly to run a plug-in on a site.
As always, you should run periodic updates for your web browser, the OS itself and your malware scanner (assuming you use one).
Is using Chrome Incognito mode the right solution?
No. Incognito was designed to prevent leaving traces on your computer, not to protect it from malicious websites.