If its a real VPS you should be able to manage it by remote desktop and use IIS directly. They typically put plesk on there so you could do hosting reseller stuff, but I would disable all of that because it uses resources and if your VPS has 500MB of RAM thats really barely enough to run IIS and SqlExpress, it doesn't have much headroom. Plesk and reseller might work for a few sites if they were all just static html sites.
I've used a VPS like that for a while at 1and1.com, I recall there was some initial confusion because they had everything locked down, to run the site you had to open a port in the firewall and other stuff, it was documented in their manuals but at first I didn't read the manuals because I'm very familiar with servers and I just expected it t work.
If they don't give you access to remote desktop and IIS I would look for a different VPS package, but don't get anything less than 500MB of RAM and if you can get more I would.
Hope it helps,
Joe