First, you should really consider selling your license to someone else and replacing it with SBS. SBS is less expensive (though the Client Access Licenses are more expensive). In addition, SBS was designed to work with small businesses - it uses wizards that are much easier for the less technically savvy to use in configuring the server.
Now it's not clear exactly what you are talking about - "i need to install MS-OFFICE and other programs on the server,so any body on the LAN can use them (client server)" - to me, this means you expect to install the programs (run setup) on the server and install them there. Then, you expect everyone on the network to be able to use them on their own computers. If that's what you mean, then you are seriously misunderstanding this. A single copy of office CANNOT be installed on the server and have more than one user at a time use it. There are license issues. Further, things just don't work that way with most software. You can use the server as a deployment point - deploying it using Active Directory (AD) and doing so would make it resilient, meaning if joe user deleted winword.exe, instead of getting an error the next time he used it, he would get a slight delay as the workstation went back to the server and downloaded the missing executable file. (Deploying it with AD is an automated way to install it to multiple workstations without having to go to each one).
Now if you mean to use the the server as a Terminal Server or GRID system, that's another story, but you STILL require a license for EVERY user who is going to use the software (exact licensing may be different - for example, rather than a license for each user, you may just need a license for each workstation, or for the number of Terminal Server Client Access Licenses (TSCALs) you have. Whatever the case, this is not as simple as you appear to be thinking it is. I strongly recommend you contact an EXPERIENCED consultant who can make recommendations and perform the overall installation and high-level management.
To put things another way... do you know much about cars? Most people I know only know enough to check tire pressure add and MAYBE change their oil. So how foolish do you think it would be, if you were a taxi company and decided to rebuild your own engines when everyone on staff, at best, only knew how to change their oil? They would EXTREMELY lucky to do it right and would take them a lot of time to figure out how to do it and do it repeatedly and reliably. They could do it, absolutely, but how many hours would the cars be unavailable to make money while the VERY amateur mechanics tried to repair things? Wouldn't it make sense to have a pro do the maintenance in a couple of hours, or at worst (in changing an engine) a day, so they could get back on the road ASAP to make money? Computers aren't cars and you're probably not a taxi business, but it's just as foolish to try to install your own network - the number of things you get wrong could waste SERIOUS time that you could be using elsewhere making money - more money than the cost of hiring a pro to do it for you.