Lobster Lake is a nice destination. The Lake has numerous nice campsites. Most folks try to stay at Ogden Point (if memory serves). It is a nice site with beach on two sides. The lake is easily accessible and with motorized craft. Typical put-in at at the Lobster Launch on Lobster Stream. There is a parking lot there. The paddle from there to the lake is a quick one, perhaps an hour or so...give or take and depending upon where you head.
You might also opt to put in upstream somewhere on the Penobscot if you chose.. North East Carry, Seboomook etc....
You can enter from the Rockwood side either coming up from Greenville or from Jackman ....your entry point to North Maine Woods (NMW) controlled roads should be at 20 Mile....you have a couple options for how to get there depending upon whether you are coming from the South (Greenville) or West (Jackman). Once you pay your fees at 20 mile (if you are putting in at Little Lobster) you will head East and go through the electronic gate. You will need your receipt to get through it so be sure that you have been to 20 Mile first..... Once through the gate you will eventually pass the NE Carry and if you opt, a small store at the head of Moosehead (gas up there if you need it!).
Here is a link to North Woods. You should be able to find everything you need. If not, call them. Be careful with the gate attendee at 20 mile...this is his first summer and unlike the experienced folks on the other side (Caribou, Telos) he's not 100% dialed in to what is where.
http://www.northmainewoods.org/ Also expect pretty rough roads inside the electronic gate.... If you call....ask for Al Coperthwaite...
All of that said, if you are looking for a paddle, may I suggest that you put in at Little Lobster, spend a day or so poking around and then paddle down the Penobscot to Chesuncook Lake. You will get there in one day w/o angst. If the weather is good and the lake is happy a campsite on Gero Island is my recommendation. If not then there are other sites before you enter the lake. There's also this
http://www.greatnorthernvacations.com/Lodging-.html They offer a shuttle if you choose to stay there.
I would then head down Chesuncook and down to Ripogenus...you should be able to organize shuttles and pickups without too much trouble.
If you opt for this route, just be aware that the prevailing wind on Chesuncook blows up the lake. It can be a beast.
Alternatively carry through Mud Pond and enter the Allagash waterway and either head down to Telos or up to Allagash...lot's of options...if you want to do a bit more.