I am goig to remodel the master bathroom and would like to know do people expect a shower and a tub or can I convert my existing tub to a larger shower/tub combo with a jet tub and with seemless glass doors. The exiting shower is small and would be converted to a linen closet.

We have in our home for 10 years the orginal owners and plan to stay in our home for at least another 5-10 years.

The value of the house is about 150K

A few thoughts on this.
If your going to stay in your home another 5 plus years do what ever you like as your living in the home. In five years there will be something new to add or change anyway so why not enjoy your home while you live there.

As far as making the tub larger and putting the shower within it. This answer depends on several factors.
1. Is the tub/shower going to be easy to enter and exit?
2. What type of community is the house located? Aging adult or young family?
3. Do you really need a jet tub or is it something that you always wanted to have? Jet tubs can be expensive to fill and sometimes often difficult to keep clean and sanitized. Most tubs that are put in these days oftentimes only get used once or twice a year if at all.
4. When re-doing a bathroom one has to consider the use in which the original bath was for. If you only have one bath its very important that you have at least one tub in the home. People with young children will need to be able to put their child into the tub and bath them without worrying about them drowning. So if you only have one tub you should be careful not to make this to large and difficult to bath small children in.
If you have a second bath and the one your changing is a master. Then change and design it for your personal pleasure.
Remember to keep the color style in such a way that it can be personalized by anyone that would purchase your home. Wild crazy colors oftentimes detract from the value of the room.
Stay away from stone and heavy look materials if the room is small. Not only are they expensive but make the room look smaller.