Taking the computer to repairman

I need to take my computer to add memory. I will have to separate from my computer for a day or two.
The problem is that many pages remember my password at login. I can logout from gmail, paypal, payoneer and a few more, but there are still dozens of websites that are logged on or remember the password at the password field. Also, all my bookmarks are visible, browsing history and files.
How can I protect myself from the computer repairman?

Thanks.

Buy the memory and add it by yourself...it's pretty easy you should have some free slot inside the pc...just take the case off and attach it..

You can clear the internet browser cache. That should do it.
Or as sebolla mentioned, replace the ram yourself.

The DIY idea is good. I save the installation fee as well, but may lose lifetime warranty.
The cost of the installation is half of the cost of the RAM, so I can take the risk.
My repairman will be very offended, though.

Add RAM to the PC is a 3 minute job. You only have to care the the RAM is the right one for your system when buying.
Do it yourself or ask a friend, it's really very easy !