Let me to try to address your questions:
however I have some questions regarding to the plan features... it shows there's a $50 per month per processor fee for MSSql database... does it apply if we installed the Sql Server ourselves using our own license key? How about using the Sql Express edition?
If you install MSSQL server with your license key or use MSSQL Express Edition, there will be no additional fees applied to the plan.
Also, what does "Managed Hosting Lite" feature include for Windows servers? Does it do website/url uptime monitoring or something similar to that effect??
Managed Hosting Lite addon includes monitoring of the important aspects of server functinatlity like memory utlization, web server on the port 80, DNS server on your server by Lunarpages admins who will try to address their problems when they alert in our monitoring system.
Please advise, if you have any further questions. Please also note that official Lunarpages support for dedicated plans will also be happy to assist you with pre-sales questions. You can contact them via firstname.lastname@example.org.